diff --git a/CHANGELOG.md b/CHANGELOG.md
index a676a59..8b1b938 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,10 @@ Supported `polkadot-sdk` rev: `2503.0.1`
 
 - Removed the license printer from the `resolc` binary.
 
+### Fixed
+
+- solc-json-interface: Serializing of any custom key in the JSON input is only skipped if not provided.
+
 ## v0.1.0
 
 This is a development pre-release.
diff --git a/Cargo.lock b/Cargo.lock
index 92e1707..19b2fc8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8705,7 +8705,7 @@ dependencies = [
 
 [[package]]
 name = "revive-solc-json-interface"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "anyhow",
  "rayon",
diff --git a/Cargo.toml b/Cargo.toml
index b180b5b..eb7a01f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,20 +15,20 @@ rust-version = "1.85.0"
 
 [workspace.dependencies]
 resolc  = { path = "crates/resolc" }
-revive-benchmarks = { version = "0.1.0", path = "crates/benchmarks" }
-revive-builtins = { version = "0.1.0", path = "crates/builtins" }
-revive-common = { version = "0.1.0", path = "crates/common" }
-revive-differential = { version = "0.1.0", path = "crates/differential" }
-revive-integration = { version = "0.1.0", path = "crates/integration" }
-revive-linker = { version = "0.1.0", path = "crates/linker" }
-lld-sys = { version = "0.1.0", path = "crates/lld-sys" }
-revive-llvm-context = { version = "0.1.0", path = "crates/llvm-context" }
-revive-runtime-api = { version = "0.1.0", path = "crates/runtime-api" }
-revive-runner = { version = "0.1.0", path = "crates/runner" }
-revive-solc-json-interface = { version = "0.1.0", path = "crates/solc-json-interface" }
-revive-stdlib = { version = "0.1.0", path = "crates/stdlib" }
-revive-build-utils = { version = "0.1.0", path = "crates/build-utils" }
-revive-yul = { version = "0.1.0", path = "crates/yul" }
+revive-benchmarks = { path = "crates/benchmarks" }
+revive-builtins = { path = "crates/builtins" }
+revive-common = { path = "crates/common" }
+revive-differential = { path = "crates/differential" }
+revive-integration = { path = "crates/integration" }
+revive-linker = { path = "crates/linker" }
+lld-sys = { path = "crates/lld-sys" }
+revive-llvm-context = { path = "crates/llvm-context" }
+revive-runtime-api = { path = "crates/runtime-api" }
+revive-runner = { path = "crates/runner" }
+revive-solc-json-interface = { path = "crates/solc-json-interface" }
+revive-stdlib = { path = "crates/stdlib" }
+revive-build-utils = { path = "crates/build-utils" }
+revive-yul = { path = "crates/yul" }
 
 hex = "0.4.3"
 cc = "1.2"
diff --git a/crates/llvm-context/src/polkavm/context/function/runtime/entry.rs b/crates/llvm-context/src/polkavm/context/function/runtime/entry.rs
index 33600ba..ae40a99 100644
--- a/crates/llvm-context/src/polkavm/context/function/runtime/entry.rs
+++ b/crates/llvm-context/src/polkavm/context/function/runtime/entry.rs
@@ -1,6 +1,7 @@
 //! The entry function.
 
 use inkwell::types::BasicType;
+use revive_solc_json_interface::PolkaVMDefaultHeapMemorySize;
 
 use crate::polkavm::context::address_space::AddressSpace;
 use crate::polkavm::context::function::runtime;
@@ -38,9 +39,12 @@ impl Entry {
             context.xlen_type().const_zero(),
         );
 
-        let heap_memory_type = context
-            .byte_type()
-            .array_type(context.memory_config.heap_size);
+        let heap_memory_type = context.byte_type().array_type(
+            context
+                .memory_config
+                .heap_size
+                .unwrap_or(PolkaVMDefaultHeapMemorySize),
+        );
         context.set_global(
             crate::polkavm::GLOBAL_HEAP_MEMORY,
             heap_memory_type,
diff --git a/crates/llvm-context/src/polkavm/context/mod.rs b/crates/llvm-context/src/polkavm/context/mod.rs
index be05a66..368c390 100644
--- a/crates/llvm-context/src/polkavm/context/mod.rs
+++ b/crates/llvm-context/src/polkavm/context/mod.rs
@@ -25,6 +25,8 @@ use inkwell::debug_info::AsDIScope;
 use inkwell::debug_info::DIScope;
 use inkwell::types::BasicType;
 use inkwell::values::BasicValue;
+use revive_solc_json_interface::PolkaVMDefaultHeapMemorySize;
+use revive_solc_json_interface::PolkaVMDefaultStackMemorySize;
 use revive_solc_json_interface::SolcStandardJsonInputSettingsPolkaVMMemory;
 
 use crate::optimizer::settings::Settings as OptimizerSettings;
@@ -233,7 +235,13 @@ where
         Self::set_data_layout(llvm, &module);
         Self::link_stdlib_module(llvm, &module);
         Self::link_polkavm_imports(llvm, &module);
-        Self::set_polkavm_stack_size(llvm, &module, memory_config.stack_size);
+        Self::set_polkavm_stack_size(
+            llvm,
+            &module,
+            memory_config
+                .stack_size
+                .unwrap_or(PolkaVMDefaultStackMemorySize),
+        );
         Self::set_module_flags(llvm, &module);
 
         let intrinsics = Intrinsics::new(llvm, &module);
@@ -1443,7 +1451,11 @@ where
     }
 
     pub fn heap_size(&self) -> inkwell::values::IntValue<'ctx> {
-        self.xlen_type()
-            .const_int(self.memory_config.heap_size as u64, false)
+        self.xlen_type().const_int(
+            self.memory_config
+                .heap_size
+                .unwrap_or(PolkaVMDefaultHeapMemorySize) as u64,
+            false,
+        )
     }
 }
diff --git a/crates/resolc/src/lib.rs b/crates/resolc/src/lib.rs
index d705f23..145f89f 100644
--- a/crates/resolc/src/lib.rs
+++ b/crates/resolc/src/lib.rs
@@ -229,7 +229,7 @@ pub fn standard_json<T: Compiler>(
         revive_llvm_context::OptimizerSettings::try_from(&solc_input.settings.optimizer)?;
 
     let polkavm_settings = solc_input.settings.polkavm.unwrap_or_default();
-    debug_config.emit_debug_info = polkavm_settings.debug_information;
+    debug_config.emit_debug_info = polkavm_settings.debug_information.unwrap_or_default();
 
     let include_metadata_hash = match solc_input.settings.metadata {
         Some(ref metadata) => metadata.bytecode_hash != Some(MetadataHash::None),
@@ -265,7 +265,9 @@ pub fn standard_json<T: Compiler>(
             include_metadata_hash,
             debug_config,
             llvm_arguments,
-            polkavm_settings.memory_config,
+            polkavm_settings
+                .memory_config
+                .unwrap_or_else(SolcStandardJsonInputSettingsPolkaVMMemory::default),
         )?;
         build.write_to_standard_json(&mut solc_output, &solc_version)?;
     }
diff --git a/crates/resolc/src/resolc/main.rs b/crates/resolc/src/resolc/main.rs
index d24063e..f22ad72 100644
--- a/crates/resolc/src/resolc/main.rs
+++ b/crates/resolc/src/resolc/main.rs
@@ -142,14 +142,10 @@ fn main_inner() -> anyhow::Result<()> {
         None => true,
     };
 
-    let mut memory_config =
-        revive_solc_json_interface::SolcStandardJsonInputSettingsPolkaVMMemory::default();
-    if let Some(heap_size) = arguments.heap_size {
-        memory_config.heap_size = heap_size
-    }
-    if let Some(stack_size) = arguments.stack_size {
-        memory_config.stack_size = stack_size
-    }
+    let memory_config = revive_solc_json_interface::SolcStandardJsonInputSettingsPolkaVMMemory::new(
+        arguments.heap_size,
+        arguments.stack_size,
+    );
 
     let build = if arguments.yul {
         resolc::yul(
diff --git a/crates/solc-json-interface/Cargo.toml b/crates/solc-json-interface/Cargo.toml
index c25fcf8..4e7093c 100644
--- a/crates/solc-json-interface/Cargo.toml
+++ b/crates/solc-json-interface/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "revive-solc-json-interface"
-version.workspace = true
+version = "0.2.0"
 authors.workspace = true
 license.workspace = true
 edition.workspace = true
@@ -20,4 +20,4 @@ anyhow = { workspace = true }
 rayon = { workspace = true, optional = true }
 semver = { workspace = true }
 serde = { workspace = true }
-serde_json = { workspace = true }
\ No newline at end of file
+serde_json = { workspace = true }
diff --git a/crates/solc-json-interface/src/lib.rs b/crates/solc-json-interface/src/lib.rs
index c34f887..7821f40 100644
--- a/crates/solc-json-interface/src/lib.rs
+++ b/crates/solc-json-interface/src/lib.rs
@@ -9,6 +9,8 @@ pub use self::standard_json::input::settings::metadata::Metadata as SolcStandard
 pub use self::standard_json::input::settings::metadata_hash::MetadataHash as SolcStandardJsonInputSettingsMetadataHash;
 pub use self::standard_json::input::settings::optimizer::Optimizer as SolcStandardJsonInputSettingsOptimizer;
 pub use self::standard_json::input::settings::polkavm::memory::MemoryConfig as SolcStandardJsonInputSettingsPolkaVMMemory;
+pub use self::standard_json::input::settings::polkavm::memory::DEFAULT_HEAP_SIZE as PolkaVMDefaultHeapMemorySize;
+pub use self::standard_json::input::settings::polkavm::memory::DEFAULT_STACK_SIZE as PolkaVMDefaultStackMemorySize;
 pub use self::standard_json::input::settings::polkavm::PolkaVM as SolcStandardJsonInputSettingsPolkaVM;
 pub use self::standard_json::input::settings::selection::file::flag::Flag as SolcStandardJsonInputSettingsSelectionFileFlag;
 pub use self::standard_json::input::settings::selection::file::File as SolcStandardJsonInputSettingsSelectionFile;
diff --git a/crates/solc-json-interface/src/standard_json/input/settings/mod.rs b/crates/solc-json-interface/src/standard_json/input/settings/mod.rs
index 683b5bd..2735d18 100644
--- a/crates/solc-json-interface/src/standard_json/input/settings/mod.rs
+++ b/crates/solc-json-interface/src/standard_json/input/settings/mod.rs
@@ -46,7 +46,7 @@ pub struct Settings {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub metadata: Option<Metadata>,
     /// The resolc custom PolkaVM settings.
-    #[serde(skip_serializing)]
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub polkavm: Option<PolkaVM>,
 }
 
@@ -75,6 +75,7 @@ impl Settings {
 
     /// Sets the necessary defaults.
     pub fn normalize(&mut self, version: &semver::Version) {
+        self.polkavm = None;
         self.optimizer.normalize(version);
     }
 
diff --git a/crates/solc-json-interface/src/standard_json/input/settings/optimizer/mod.rs b/crates/solc-json-interface/src/standard_json/input/settings/optimizer/mod.rs
index 080ad27..3b6d0c3 100644
--- a/crates/solc-json-interface/src/standard_json/input/settings/optimizer/mod.rs
+++ b/crates/solc-json-interface/src/standard_json/input/settings/optimizer/mod.rs
@@ -14,13 +14,13 @@ pub struct Optimizer {
     /// Whether the optimizer is enabled.
     pub enabled: bool,
     /// The optimization mode string.
-    #[serde(skip_serializing)]
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub mode: Option<char>,
     /// The `solc` optimizer details.
     #[serde(skip_serializing_if = "Option::is_none")]
     pub details: Option<Details>,
     /// Whether to try to recompile with -Oz if the bytecode is too large.
-    #[serde(skip_serializing)]
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub fallback_to_optimizing_for_size: Option<bool>,
 }
 
@@ -42,6 +42,8 @@ impl Optimizer {
 
     /// Sets the necessary defaults.
     pub fn normalize(&mut self, version: &semver::Version) {
+        self.mode = None;
+        self.fallback_to_optimizing_for_size = None;
         self.details = if version >= &semver::Version::new(0, 5, 5) {
             Some(Details::disabled(version))
         } else {
diff --git a/crates/solc-json-interface/src/standard_json/input/settings/polkavm/memory.rs b/crates/solc-json-interface/src/standard_json/input/settings/polkavm/memory.rs
index 87fc695..573b0c4 100644
--- a/crates/solc-json-interface/src/standard_json/input/settings/polkavm/memory.rs
+++ b/crates/solc-json-interface/src/standard_json/input/settings/polkavm/memory.rs
@@ -2,20 +2,35 @@
 
 use serde::{Deserialize, Serialize};
 
+pub const DEFAULT_HEAP_SIZE: u32 = 64 * 1024;
+pub const DEFAULT_STACK_SIZE: u32 = 32 * 1024;
+
 /// The PolkaVM memory configuration.
 #[derive(Clone, Copy, Debug, Deserialize, Serialize)]
 pub struct MemoryConfig {
     /// The emulated EVM linear heap memory size in bytes.
-    pub heap_size: u32,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub heap_size: Option<u32>,
     /// The PVM stack size in bytes.
-    pub stack_size: u32,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub stack_size: Option<u32>,
+}
+
+impl MemoryConfig {
+    /// A shorthand constructor.
+    pub fn new(heap_size: Option<u32>, stack_size: Option<u32>) -> Self {
+        Self {
+            heap_size,
+            stack_size,
+        }
+    }
 }
 
 impl Default for MemoryConfig {
     fn default() -> Self {
         Self {
-            heap_size: 64 * 1024,
-            stack_size: 32 * 1024,
+            heap_size: Some(DEFAULT_HEAP_SIZE),
+            stack_size: Some(DEFAULT_STACK_SIZE),
         }
     }
 }
diff --git a/crates/solc-json-interface/src/standard_json/input/settings/polkavm/mod.rs b/crates/solc-json-interface/src/standard_json/input/settings/polkavm/mod.rs
index 2ed7f16..6e806e1 100644
--- a/crates/solc-json-interface/src/standard_json/input/settings/polkavm/mod.rs
+++ b/crates/solc-json-interface/src/standard_json/input/settings/polkavm/mod.rs
@@ -11,16 +11,18 @@ pub mod memory;
 #[derive(Clone, Copy, Default, Debug, Serialize, Deserialize)]
 pub struct PolkaVM {
     /// The PolkaVM target machine memory configuration settings.
-    pub memory_config: MemoryConfig,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub memory_config: Option<MemoryConfig>,
     /// Instruct LLVM to emit debug information.
-    pub debug_information: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub debug_information: Option<bool>,
 }
 
 impl PolkaVM {
     pub fn new(memory_config: Option<MemoryConfig>, debug_information: bool) -> Self {
         Self {
-            memory_config: memory_config.unwrap_or_default(),
-            debug_information,
+            memory_config,
+            debug_information: Some(debug_information),
         }
     }
 }