diff --git a/crates/integration/contracts/MSize.sol b/crates/integration/contracts/MSize.sol
new file mode 100644
index 0000000..b7a22ad
--- /dev/null
+++ b/crates/integration/contracts/MSize.sol
@@ -0,0 +1,9 @@
+contract MSize {
+    uint[] public data;
+
+    function mSize() public pure returns (uint size) {
+        assembly {
+            size := msize()
+        }
+    }
+}
diff --git a/crates/integration/src/lib.rs b/crates/integration/src/lib.rs
index 31b70af..7d62110 100644
--- a/crates/integration/src/lib.rs
+++ b/crates/integration/src/lib.rs
@@ -1,14 +1,26 @@
 pub mod mock_runtime;
 
+/// Compile the blob of `contract_name` found in given `source_code`.
+/// The `solc` optimizer will be enabled
 pub fn compile_blob(contract_name: &str, source_code: &str) -> Vec<u8> {
+    compile_blob_with_options(contract_name, source_code, true)
+}
+
+/// Compile the blob of `contract_name` found in given `source_code`.
+pub fn compile_blob_with_options(
+    contract_name: &str,
+    source_code: &str,
+    solc_optimizer_enabled: bool,
+) -> Vec<u8> {
     let file_name = "contract.sol";
 
-    let contracts = revive_solidity::test_utils::build_solidity(
+    let contracts = revive_solidity::test_utils::build_solidity_with_options(
         [(file_name.into(), source_code.into())].into(),
         Default::default(),
         None,
         revive_solidity::SolcPipeline::Yul,
         era_compiler_llvm_context::OptimizerSettings::cycles(),
+        solc_optimizer_enabled,
     )
     .expect("source should compile")
     .contracts
@@ -149,4 +161,30 @@ mod tests {
         let received = I256::from_be_bytes::<32>(state.output.data.try_into().unwrap());
         assert_eq!(received, expected);
     }
+
+    #[test]
+    fn msize() {
+        sol!(
+            #[derive(Debug, PartialEq, Eq)]
+            contract MSize {
+                function mSize() public pure returns (uint);
+            }
+        );
+        let code = crate::compile_blob_with_options(
+            "MSize",
+            include_str!("../contracts/MSize.sol"),
+            false,
+        );
+
+        let input = MSize::mSizeCall::new(()).abi_encode();
+        let (instance, export) = mock_runtime::prepare(&code, None);
+        let state = crate::mock_runtime::call(State::new(input), &instance, export);
+
+        assert_eq!(state.output.flags, 0);
+
+        // Solidity always stores the "free memory pointer" (32 byte int) at offset 64.
+        let expected = U256::try_from(64 + 32).unwrap();
+        let received = U256::from_be_bytes::<32>(state.output.data.try_into().unwrap());
+        assert_eq!(received, expected);
+    }
 }
diff --git a/crates/llvm-context/src/eravm/evm/context.rs b/crates/llvm-context/src/eravm/evm/context.rs
index 374bee2..682ac76 100644
--- a/crates/llvm-context/src/eravm/evm/context.rs
+++ b/crates/llvm-context/src/eravm/evm/context.rs
@@ -2,6 +2,8 @@
 //! Translates the context getter instructions.
 //!
 
+use inkwell::values::BasicValue;
+
 use crate::eravm::context::Context;
 use crate::eravm::Dependency;
 
@@ -180,10 +182,24 @@ where
 /// Translates the `msize` instruction.
 ///
 pub fn msize<'ctx, D>(
-    _context: &mut Context<'ctx, D>,
+    context: &mut Context<'ctx, D>,
 ) -> anyhow::Result<inkwell::values::BasicValueEnum<'ctx>>
 where
     D: Dependency + Clone,
 {
-    todo!()
+    let heap_end = context.build_sbrk(context.xlen_type().const_zero())?;
+    let heap_start = context
+        .get_global(crate::eravm::GLOBAL_HEAP_MEMORY_POINTER)?
+        .value
+        .as_pointer_value();
+    let heap_size = context.builder().build_int_nuw_sub(
+        context
+            .builder()
+            .build_ptr_to_int(heap_end, context.xlen_type(), "heap_end")?,
+        context
+            .builder()
+            .build_ptr_to_int(heap_start, context.xlen_type(), "heap_start")?,
+        "heap_size",
+    )?;
+    Ok(heap_size.as_basic_value_enum())
 }
diff --git a/crates/solidity/src/test_utils.rs b/crates/solidity/src/test_utils.rs
index bf2bd24..da82478 100644
--- a/crates/solidity/src/test_utils.rs
+++ b/crates/solidity/src/test_utils.rs
@@ -30,15 +30,34 @@ fn check_dependencies() {
     }
 }
 
-///
 /// Builds the Solidity project and returns the standard JSON output.
-///
 pub fn build_solidity(
     sources: BTreeMap<String, String>,
     libraries: BTreeMap<String, BTreeMap<String, String>>,
     remappings: Option<BTreeSet<String>>,
     pipeline: SolcPipeline,
     optimizer_settings: era_compiler_llvm_context::OptimizerSettings,
+) -> anyhow::Result<SolcStandardJsonOutput> {
+    build_solidity_with_options(
+        sources,
+        libraries,
+        remappings,
+        pipeline,
+        optimizer_settings,
+        true,
+    )
+}
+
+/// Builds the Solidity project and returns the standard JSON output.
+/// Gives control over additional options:
+/// - `solc_optimizer_enabled`: Whether to use the `solc` optimizer
+pub fn build_solidity_with_options(
+    sources: BTreeMap<String, String>,
+    libraries: BTreeMap<String, BTreeMap<String, String>>,
+    remappings: Option<BTreeSet<String>>,
+    pipeline: SolcPipeline,
+    optimizer_settings: era_compiler_llvm_context::OptimizerSettings,
+    solc_optimizer_enabled: bool,
 ) -> anyhow::Result<SolcStandardJsonOutput> {
     check_dependencies();
 
@@ -56,7 +75,7 @@ pub fn build_solidity(
         remappings,
         SolcStandardJsonInputSettingsSelection::new_required(pipeline),
         SolcStandardJsonInputSettingsOptimizer::new(
-            true,
+            solc_optimizer_enabled,
             None,
             &solc_version.default,
             false,