diff --git a/src/runtime/Memory.cpp b/src/runtime/Memory.cpp
index 71eafbaf8..184175fcb 100644
--- a/src/runtime/Memory.cpp
+++ b/src/runtime/Memory.cpp
@@ -43,7 +43,7 @@ Memory::Memory(uint64_t initialSizeInByte, uint64_t maximumSizeInByte, bool isSh
     , m_targetBuffers(nullptr)
     , m_isShared(isShared)
 {
-    ASSERT(initialSizeInByte <= std::numeric_limits<size_t>::max());
+    RELEASE_ASSERT(initialSizeInByte <= std::numeric_limits<size_t>::max());
 #if defined(WALRUS_USE_MMAP)
     if (m_maximumSizeInByte) {
 #ifndef WALRUS_32_MEMORY_INITIAL_MMAP_RESERVED_ADDRESS_SIZE
@@ -58,7 +58,7 @@ Memory::Memory(uint64_t initialSizeInByte, uint64_t maximumSizeInByte, bool isSh
 #else
             WALRUS_64_MEMORY_INITIAL_MMAP_RESERVED_ADDRESS_SIZE;
 #endif
-        m_reservedSizeInByte = std::min(initialReservedSize, m_maximumSizeInByte);
+        m_reservedSizeInByte = std::min(std::max(initialReservedSize, initialSizeInByte), m_maximumSizeInByte);
         m_buffer = reinterpret_cast<uint8_t*>(mmap(NULL, m_reservedSizeInByte, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
         RELEASE_ASSERT(MAP_FAILED != m_buffer);
         mprotect(m_buffer, initialSizeInByte, (PROT_READ | PROT_WRITE));
diff --git a/test/jit/memory_large.wast b/test/jit/memory_large.wast
new file mode 100644
index 000000000..91f9a706f
--- /dev/null
+++ b/test/jit/memory_large.wast
@@ -0,0 +1,19 @@
+(module
+    (; 1GB memory, can be quite large for a 32 bit system. ;)
+    (memory 16384 16384)
+
+    (func (export "set") (param i32 i32)
+        local.get 0
+        local.get 1
+        i32.store8
+    )
+
+    (func (export "get") (param i32) (result i32)
+        local.get 0
+        i32.load8_u
+    )
+)
+
+(invoke "set" (i32.const 0x3fffffff) (i32.const 0xaa))
+(assert_return (invoke "get" (i32.const 0x3fffffff)) (i32.const 0xaa))
+(assert_trap (invoke "get" (i32.const 0x40000000)) "out of bounds memory access")