diff --git a/libsolidity/codegen/YulUtilFunctions.cpp b/libsolidity/codegen/YulUtilFunctions.cpp
index 8abc2385f..ea3fec01b 100644
--- a/libsolidity/codegen/YulUtilFunctions.cpp
+++ b/libsolidity/codegen/YulUtilFunctions.cpp
@@ -2353,8 +2353,6 @@ string YulUtilFunctions::copyArrayFromStorageToMemoryFunction(ArrayType const& _
 
 string YulUtilFunctions::mappingIndexAccessFunction(MappingType const& _mappingType, Type const& _keyType)
 {
-	solAssert(_keyType.sizeOnStack() <= 1, "");
-
 	string functionName = "mapping_index_access_" + _mappingType.identifier() + "_of_" + _keyType.identifier();
 	return m_functionCollector.createFunction(functionName, [&]() {
 		if (_mappingType.keyType()->isDynamicallySized())
@@ -2364,7 +2362,7 @@ string YulUtilFunctions::mappingIndexAccessFunction(MappingType const& _mappingT
 				}
 			)")
 			("functionName", functionName)
-			("key", _keyType.sizeOnStack() > 0 ? "key" : "")
+			("key", suffixedVariableNameList("key_", 0, _keyType.sizeOnStack()))
 			("hash", packedHashFunction(
 				{&_keyType, TypeProvider::uint256()},
 				{_mappingType.keyType(), TypeProvider::uint256()}
diff --git a/libsolidity/codegen/ir/IRGeneratorForStatements.cpp b/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
index 691724e1b..c2a54a838 100644
--- a/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
+++ b/libsolidity/codegen/ir/IRGeneratorForStatements.cpp
@@ -2062,7 +2062,6 @@ void IRGeneratorForStatements::endVisit(IndexAccess const& _indexAccess)
 
 		MappingType const& mappingType = dynamic_cast<MappingType const&>(baseType);
 		Type const& keyType = *_indexAccess.indexExpression()->annotation().type;
-		solAssert(keyType.sizeOnStack() <= 1, "");
 
 		string slot = m_context.newYulVariable();
 		Whiskers templ("let <slot> := <indexAccess>(<base><?+key>,<key></+key>)\n");
diff --git a/test/libsolidity/semanticTests/storage/mapping_string_key.sol b/test/libsolidity/semanticTests/storage/mapping_string_key.sol
new file mode 100644
index 000000000..84ac9b09a
--- /dev/null
+++ b/test/libsolidity/semanticTests/storage/mapping_string_key.sol
@@ -0,0 +1,24 @@
+contract C {
+    mapping (string => uint) m_nameToRecord;
+    function set(string calldata key, uint value) external {
+        m_nameToRecord[key] = value;
+    }
+    function get(string calldata key) external view returns (uint) {
+        return m_nameToRecord[key];
+    }
+    function setFixed(uint value) external {
+        m_nameToRecord["fixed"] = value;
+    }
+    function getFixed() external view returns (uint) {
+        return m_nameToRecord["fixed"];
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// set(string,uint256): 0x40, 8, 3, "abc" ->
+// get(string): 0x20, 3, "abc" -> 8
+// get(string): 0x20, 3, "abe" -> 0
+// getFixed() -> 0
+// setFixed(uint256): 9 ->
+// getFixed() -> 9