diff --git a/build/jam/ArchitectureRules b/build/jam/ArchitectureRules
index 5a838867d7..4bfb17d9a9 100644
--- a/build/jam/ArchitectureRules
+++ b/build/jam/ArchitectureRules
@@ -125,6 +125,16 @@ rule ArchitectureSetup architecture
 		-Wno-ctor-dtor-privacy -Woverloaded-virtual -Wpointer-arith -Wcast-align
 		-Wsign-compare -Wno-multichar ;
 
+	HAIKU_WERROR_FLAGS_$(architecture) = ;
+
+	if $(gccVersion[1]) >= 4 {
+		# -Wuninitialized gives too many false positives.
+		HAIKU_WERROR_FLAGS_$(architecture) += -Wno-error=uninitialized ;
+
+		# TODO: remove the -Wno-unused-but-set-variable option
+		HAIKU_WERROR_FLAGS_$(architecture) += -Wno-unused-but-set-variable ;
+	}
+
 	# debug flags
 	local debugFlags = -ggdb ;
 
@@ -459,32 +469,18 @@ rule ArchitectureSetupWarnings architecture
 				# we use #warning as placeholders for things to write...
 	}
 
-
 	# enable -Werror for certain parts of the source tree
-	HAIKU_WERRORFLAGS = ;
-	local gccVersion = $(HAIKU_GCC_VERSION_$(architecture)) ;
-	if $(gccVersion[1]) >= 4 {
-		# -Wuninitialized gives too many false positives.
-		HAIKU_WERRORFLAGS = -Wno-error=uninitialized ;
-
-		# TODO: remove the -Wno-unused-but-set-variable option
-		HAIKU_WERRORFLAGS += -Wno-unused-but-set-variable ;
-	}
-
 	HAIKU_WERROR_ARCH = $(architecture) ;
 
 	rule EnableWerror dirTokens : scope {
-		AppendToConfigVar TARGET_WARNING_CCFLAGS_$(HAIKU_WERROR_ARCH)
-			: HAIKU_TOP $(dirTokens)
-			: -Werror $(HAIKU_WERRORFLAGS) : $(scope) ;
-		AppendToConfigVar TARGET_WARNING_C++FLAGS_$(HAIKU_WERROR_ARCH)
-			: HAIKU_TOP $(dirTokens)
-			: -Werror $(HAIKU_WERRORFLAGS) : $(scope) ;
+		SetConfigVar WARNINGS : HAIKU_TOP $(dirTokens) : treatAsErrors
+			: $(scope) ;
 	}
 
 	# Work-around for GCC 2 problem -- despite -Wno-multichar it reports
 	# multichar warnings in headers/private/kernel/debugger_keymaps.h included
 	# by src/system/kernel/arch/x86/arch_debug_console.cpp.
+	local gccVersion = $(HAIKU_GCC_VERSION_$(architecture)) ;
 	if $(gccVersion[1]) = 2 {
 		local file = <src!system!kernel!arch!x86>arch_debug_console.o ;
 		TARGET_WARNING_C++FLAGS_$(architecture) on $(file)
diff --git a/build/jam/BuildSetup b/build/jam/BuildSetup
index a435ee5c43..fa72d75516 100644
--- a/build/jam/BuildSetup
+++ b/build/jam/BuildSetup
@@ -366,6 +366,8 @@ HOST_WARNING_C++FLAGS = -Wall -Wno-trigraphs -Wno-ctor-dtor-privacy
 HOST_KERNEL_WARNING_CCFLAGS = -Wall -Wno-trigraphs -Wmissing-prototypes ;
 HOST_KERNEL_WARNING_C++FLAGS = -Wall -Wno-trigraphs ;
 
+HOST_WERROR_FLAGS = ;
+
 # debug flags
 local hostDebugFlags ;
 switch $(HOST_PLATFORM) {
@@ -671,7 +673,7 @@ local archDependentBuildVars =
 	ARFLAGS ASFLAGS UNARFLAGS CPPFLAGS CCFLAGS C++FLAGS HDRS LDFLAGS
 	LINK LINKFLAGS
 
-	WARNING_CCFLAGS WARNING_C++FLAGS
+	WARNING_CCFLAGS WARNING_C++FLAGS WERROR_FLAGS
 
 	DEBUG_$(HAIKU_DEBUG_LEVELS)_CCFLAGS DEBUG_$(HAIKU_DEBUG_LEVELS)_C++FLAGS
 
diff --git a/build/jam/MainBuildRules b/build/jam/MainBuildRules
index 5a84d5e285..ba9822077e 100644
--- a/build/jam/MainBuildRules
+++ b/build/jam/MainBuildRules
@@ -291,6 +291,9 @@ rule CreateAsmStructOffsetsHeader header : source
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(HOST_WARNING_C++FLAGS) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror $(HOST_WERROR_FLAGS) ;
+				}
 			}
 
 			# debug and other flags
@@ -311,6 +314,10 @@ rule CreateAsmStructOffsetsHeader header : source
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(TARGET_WARNING_C++FLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror
+						$(TARGET_WERROR_FLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				}
 			}
 
 			# debug and other flags
diff --git a/build/jam/OverriddenJamRules b/build/jam/OverriddenJamRules
index 50ef8ef05a..8a11b6b844 100644
--- a/build/jam/OverriddenJamRules
+++ b/build/jam/OverriddenJamRules
@@ -282,6 +282,9 @@ rule Cc
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(HOST_WARNING_CCFLAGS) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror $(HOST_WERROR_FLAGS) ;
+				}
 			}
 
 			# debug and other flags
@@ -302,6 +305,10 @@ rule Cc
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(TARGET_WARNING_CCFLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror
+						$(TARGET_WERROR_FLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				}
 			}
 
 			# debug and other flags
@@ -353,6 +360,9 @@ rule C++
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(HOST_WARNING_C++FLAGS) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror $(HOST_WERROR_FLAGS) ;
+				}
 			}
 
 			# debug and other flags
@@ -373,6 +383,10 @@ rule C++
 			# warning flags
 			if $(WARNINGS) != 0 {
 				flags += $(TARGET_WARNING_C++FLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				if $(WARNINGS) = treatAsErrors {
+					flags += -Werror
+						$(TARGET_WERROR_FLAGS_$(TARGET_PACKAGING_ARCH)) ;
+				}
 			}
 
 			# debug and other flags