diff --git a/scripts/shader.mk b/scripts/shader.mk
index 91012a5d2..56937fb10 100644
--- a/scripts/shader.mk
+++ b/scripts/shader.mk
@@ -25,6 +25,8 @@ all:
 	@echo "  TARGET=7 (spriv)"
 else
 
+ADDITIONAL_INCLUDES?=
+
 ifeq ($(TARGET), 0)
 VS_FLAGS=--platform windows -p vs_3_0 -O 3
 FS_FLAGS=--platform windows -p ps_3_0 -O 3
@@ -80,9 +82,9 @@ endif
 endif
 
 THISDIR := $(dir $(lastword $(MAKEFILE_LIST)))
-VS_FLAGS+=-i $(THISDIR)../src/
-FS_FLAGS+=-i $(THISDIR)../src/
-CS_FLAGS+=-i $(THISDIR)../src/
+VS_FLAGS+=-i $(THISDIR)../src/ $(ADDITIONAL_INCLUDES)
+FS_FLAGS+=-i $(THISDIR)../src/ $(ADDITIONAL_INCLUDES)
+CS_FLAGS+=-i $(THISDIR)../src/ $(ADDITIONAL_INCLUDES)
 
 BUILD_OUTPUT_DIR=$(addprefix ./, $(RUNTIME_DIR)/$(SHADER_PATH))
 BUILD_INTERMEDIATE_DIR=$(addprefix $(BUILD_DIR)/, $(SHADER_PATH))
diff --git a/src/bgfx_p.h b/src/bgfx_p.h
index 8025a2678..f4ab861bd 100644
--- a/src/bgfx_p.h
+++ b/src/bgfx_p.h
@@ -3006,7 +3006,7 @@ namespace bgfx
 			if (!isValid(_vsh)
 			||  !isValid(_fsh) )
 			{
-				BX_WARN(false, "Vertex/fragment shader is invalid (vsh %d, fsh %d).", _vsh.idx, _fsh.idx);
+				BX_TRACE("Vertex/fragment shader is invalid (vsh %d, fsh %d).", _vsh.idx, _fsh.idx);
 				ProgramHandle invalid = BGFX_INVALID_HANDLE;
 				return invalid;
 			}
@@ -3024,7 +3024,7 @@ namespace bgfx
 			const ShaderRef& fsr = m_shaderRef[_fsh.idx];
 			if (vsr.m_hash != fsr.m_hash)
 			{
-				BX_WARN(vsr.m_hash == fsr.m_hash, "Vertex shader output doesn't match fragment shader input.");
+				BX_TRACE("Vertex shader output doesn't match fragment shader input.");
 				ProgramHandle invalid = BGFX_INVALID_HANDLE;
 				return invalid;
 			}
diff --git a/tools/shaderc/shaderc.cpp b/tools/shaderc/shaderc.cpp
index 269c81b4e..d0004c8e2 100644
--- a/tools/shaderc/shaderc.cpp
+++ b/tools/shaderc/shaderc.cpp
@@ -422,7 +422,7 @@ namespace bgfx
 
 	struct Preprocessor
 	{
-		Preprocessor(const char* _filePath, bool _essl, const char* _includeDir = NULL)
+		Preprocessor(const char* _filePath, bool _essl)
 			: m_tagptr(m_tags)
 			, m_scratchPos(0)
 			, m_fgetsPos(0)
@@ -459,11 +459,6 @@ namespace bgfx
 			m_tagptr->data = scratch(_filePath);
 			m_tagptr++;
 
-			if (NULL != _includeDir)
-			{
-				addInclude(_includeDir);
-			}
-
 			if (!_essl)
 			{
 				m_default = "#define lowp\n#define mediump\n#define highp\n";
@@ -869,7 +864,13 @@ namespace bgfx
 		bool preprocessOnly = cmdLine.hasArg("preprocess");
 		const char* includeDir = cmdLine.findOption('i');
 
-		Preprocessor preprocessor(filePath, 0 != essl, includeDir);
+		Preprocessor preprocessor(filePath, 0 != essl);
+
+		for (int ii = 1; NULL != includeDir; ++ii)
+		{
+			preprocessor.addInclude(includeDir);
+			includeDir = cmdLine.findOption(ii, 'i');
+		}
 
 		std::string dir;
 		{