diff --git a/build/jam/MainBuildRules b/build/jam/MainBuildRules
index ac9fded5ec..800f91ade5 100644
--- a/build/jam/MainBuildRules
+++ b/build/jam/MainBuildRules
@@ -271,6 +271,11 @@ rule CreateAsmStructOffsetsHeader header : source
 	local systemIncludesOption ;
 
 	on $(header) { # use on $(1) variable values
+		if ! $(PLATFORM) in $(SUPPORTED_PLATFORMS) {
+			Echo $(PLATFORM) is not in SUPPORTED_PLATFORMS, cannot make struct-offsets header! ;
+			return ;
+		}
+
 		# headers and defines
 		headers = $(HAIKU_CONFIG_HEADERS) $(SEARCH_SOURCE) $(SUBDIRHDRS)
 			$(HDRS) ;
diff --git a/build/jam/SystemLibraryRules b/build/jam/SystemLibraryRules
index 0310b2a6c9..d7d75cc7f7 100644
--- a/build/jam/SystemLibraryRules
+++ b/build/jam/SystemLibraryRules
@@ -22,12 +22,6 @@ rule TargetLibstdc++ asPath
 	# Returns the c++-standard-library for the target.
 	# Invoking with <asPath> = true will return the full library path.
 
-	if $(TARGET_PLATFORM) = libbe_test {
-		if $(TARGET_PACKAGING_ARCH) = x86_gcc2 {
-			return stdc++.r4 ;
-		}
-	}
-
 	if $(TARGET_PLATFORM) = haiku || $(TARGET_PLATFORM) = libbe_test {
 		if $(TARGET_PACKAGING_ARCH) = x86_gcc2 {
 			# the libstdc++.so for our legacy compiler (needs to be built)
diff --git a/src/libs/stdc++/legacy/Jamfile b/src/libs/stdc++/legacy/Jamfile
index 26637ff21d..53e89366b4 100644
--- a/src/libs/stdc++/legacy/Jamfile
+++ b/src/libs/stdc++/legacy/Jamfile
@@ -1,5 +1,7 @@
 SubDir HAIKU_TOP src libs stdc++ legacy ;
 
+AddSubDirSupportedPlatforms libbe_test ;
+
 local architectureObject ;
 for architectureObject in [ MultiArchSubDirSetup x86_gcc2 ] {
 	on $(architectureObject) {