diff --git a/core/relinker/CMakeLists.txt b/core/relinker/CMakeLists.txt
index 4561113eb..c47fc2c5a 100644
--- a/core/relinker/CMakeLists.txt
+++ b/core/relinker/CMakeLists.txt
@@ -144,6 +144,22 @@ if(BUILD_TESTING)
     target_include_directories(autorun_exit_tests PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/cli/include ${CMAKE_CURRENT_SOURCE_DIR}/io/include ${CMAKE_CURRENT_SOURCE_DIR}/domain/include)
     add_test(NAME autorun_exit_status COMMAND autorun_exit_tests)
     set_tests_properties(autorun_exit_status PROPERTIES TIMEOUT 20)
+    add_test_executable(rewrite_boundaries_tests
+        ${CMAKE_CURRENT_SOURCE_DIR}/codegen/tests/RewriteBoundaryTests.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/x86/X64InstructionRewriter.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/InstructionScanner.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/x86/X64InstructionDecoder.cpp
+    )
+    target_include_directories(rewrite_boundaries_tests PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/domain/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/relinker/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/elfpatcher/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/codegen/include
+        ${CMAKE_CURRENT_SOURCE_DIR}/io/include
+    )
+    add_test(NAME rewrite_boundaries COMMAND rewrite_boundaries_tests)
+    set_tests_properties(rewrite_boundaries PROPERTIES TIMEOUT 20)
+
     add_test_executable(cli_args_tests
         ${CMAKE_CURRENT_SOURCE_DIR}/cli/tests/CliArgsTests.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/cli/src/CliArgs.cpp
diff --git a/core/relinker/codegen/src/x86/X64InstructionRewriter.cpp b/core/relinker/codegen/src/x86/X64InstructionRewriter.cpp
index a3899c3dd..212bdaee2 100644
--- a/core/relinker/codegen/src/x86/X64InstructionRewriter.cpp
+++ b/core/relinker/codegen/src/x86/X64InstructionRewriter.cpp
@@ -74,6 +74,18 @@ RewriteResult X64InstructionRewriter::Rewrite(
         throw CodegenException("Rewrite offset is out of bounds", request.Offset);
     }
 
+    const auto scanner = MakeInstructionScanner();
+    const auto matches = scanner->ScanCodeSection(codeSection, 0, codeSection.size());
+    bool instructionStart = false;
+    for (const auto& match : matches) {
+        if (match.Offset == request.Offset) {
+            instructionStart = true;
+            break;
+        }
+    }
+    if (!instructionStart)
+        throw CodegenException("Rewrite offset is not an instruction boundary", request.Offset);
+
     const X64InstructionDecoder decoder;
     const std::size_t decodedLength = decoder.Decode(codeSection.data() + offset, codeSection.size() - offset);
 
@@ -90,9 +102,6 @@ RewriteResult X64InstructionRewriter::Rewrite(
     rewritten.insert(rewritten.end(), request.NewBytes.begin(), request.NewBytes.end());
     rewritten.insert(rewritten.end(), codeSection.begin() + offset + decodedLength, codeSection.end());
 
-    const auto scanner = MakeInstructionScanner();
-    const auto matches = scanner->ScanCodeSection(codeSection, 0, codeSection.size());
-
     std::vector<AddressAdjustment> adjustments;
 
     for (const auto& match : matches) {
diff --git a/core/relinker/codegen/tests/RewriteBoundaryTests.cpp b/core/relinker/codegen/tests/RewriteBoundaryTests.cpp
new file mode 100644
index 000000000..fa9ee0055
--- /dev/null
+++ b/core/relinker/codegen/tests/RewriteBoundaryTests.cpp
@@ -0,0 +1,27 @@
+#include <codegen/x86/X64InstructionRewriter.hpp>
+#include <iostream>
+#include <stdexcept>
+
+static void Require(bool ok) { if (!ok) throw std::runtime_error("Invalid rewrite boundary accepted"); }
+
+int main() {
+    try {
+        const Codegen::X64InstructionRewriter rewriter;
+        for (const auto& code : {std::vector<std::uint8_t>{0xB8, 0x90, 0x90, 0x90, 0x90, 0xC3},
+                               std::vector<std::uint8_t>{0x48, 0x8B, 0x05, 0x90, 0x90, 0x90, 0x90, 0xC3},
+                               std::vector<std::uint8_t>{0xE8, 0x90, 0x90, 0x90, 0x90, 0xC3}}) {
+            const auto original = code;
+            for (std::size_t offset = 1; offset + 1 < code.size(); ++offset) {
+                bool rejected = false;
+                try { (void)rewriter.Rewrite(code, {offset, {0x90}}); }
+                catch (const std::exception&) { rejected = true; }
+                Require(rejected && code == original);
+            }
+            const auto result = rewriter.Rewrite(code, {0, {0x90}});
+            Require(result.Bytes == std::vector<std::uint8_t>{0x90, 0xC3});
+        }
+        const auto result = rewriter.Rewrite({0x90, 0x90, 0xC3}, {1, {0x90, 0x90}});
+        Require(result.Bytes == std::vector<std::uint8_t>{0x90, 0x90, 0x90, 0xC3});
+        std::cout << "18 rewrite boundary cases passed\n";
+    } catch (const std::exception& error) { std::cerr << error.what() << '\n'; return 1; }
+}