diff --git a/implementations/Crafter.Build-Platform.cpp b/implementations/Crafter.Build-Platform.cpp
index f8a7694..03cdba2 100644
--- a/implementations/Crafter.Build-Platform.cpp
+++ b/implementations/Crafter.Build-Platform.cpp
@@ -845,7 +845,18 @@ Configuration Crafter::LoadProject(const fs::path& projectFile, std::span<const
     // in for the executable: project.so resolves Crafter:: symbols from the
     // running binary, so only the declarations (the .cppm files) matter,
     // and an implementation-only rebuild of crafter-build leaves it valid.
-    const std::string projectStamp = HashStamp(std::format("{}\0{}\0{}\0{}", CrafterBuildVersion(), GetToolchain().Key(), sourcesStamp, compileCmd));
+    // The separators are appended, not written into a format string: a
+    // format string is read as a C string, so one with "\0" in it ends at the
+    // first NUL and everything after the version silently dropped out of the
+    // stamp. A project.so compiled against other declarations (a Shader with
+    // a different layout, say) was then loaded as current and corrupted the
+    // heap.
+    std::string projectStampInput(CrafterBuildVersion());
+    for (std::string_view part : {std::string_view(GetToolchain().Key()), std::string_view(sourcesStamp), std::string_view(compileCmd)}) {
+        projectStampInput += '\0';
+        projectStampInput += part;
+    }
+    const std::string projectStamp = HashStamp(projectStampInput);
 
     if (ProjectFileStale(soPath, absProject, projectStamp, preDeps)) {
         std::string result = RunBuildCommand(compileCmd);