diff --git a/CMakeLists.txt b/CMakeLists.txt
index af2743c37d..582e47c698 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -146,6 +146,11 @@ if( MSVC )
 	string(REPLACE "/MD " " " CMAKE_C_FLAGS_RELWITHDEBINFO ${CMAKE_C_FLAGS_RELWITHDEBINFO} )
 	string(REPLACE "/MDd " " " CMAKE_C_FLAGS_DEBUG ${CMAKE_C_FLAGS_DEBUG} )
 	string(REPLACE " /GR" " " CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} )
+else( MSVC )
+	set( REL_LINKER_FLAGS "" )
+	set( ALL_C_FLAGS "" )
+	set( REL_C_FLAGS "" )
+	set( DEB_C_FLAGS "" )
 endif( MSVC )
 
 set( CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} ${REL_LINKER_FLAGS}" )
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5870a34fac..5d6719fba1 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -51,6 +51,20 @@ set( MINOR_VERSIONS "50" "49" "48" "47" "46" "45" "44" "43" "42" "41"
 	"15" "14" "13" "12" "11" "10" "09" "08" "07" "06" "05" "04" "03"
 	"02" "01" "00" )
 set( MAJOR_VERSIONS "44" "34" "28" "26" "24" "22" "20" )
+
+if( NOT FMOD_DIR_VERSIONS )
+	set( FMOD_DIR_VERSIONS "" )
+endif( NOT FMOD_DIR_VERSIONS )
+if( NOT FMOD_VERSIONS )
+	set( FMOD_VERSIONS "" )
+endif( NOT FMOD_VERSIONS )
+if( NOT FMOD_LOCAL_INC_DIRS )
+	set( FMOD_LOCAL_INC_DIRS "" )
+endif( NOT FMOD_LOCAL_INC_DIRS )
+if( NOT FMOD_LOCAL_LIB_DIRS )
+	set( FMOD_LOCAL_LIB_DIRS "" )
+endif( NOT FMOD_LOCAL_LIB_DIRS )
+
 set( FMOD_DIR_VERSIONS ${FMOD_DIR_VERSIONS} "../fmod" )
 foreach( majver ${MAJOR_VERSIONS} )
 	foreach( minver ${MINOR_VERSIONS} )
@@ -63,6 +77,10 @@ foreach( majver ${MAJOR_VERSIONS} )
 	endforeach( dir ${FMOD_DIR_VERSIONS} )
 endforeach( majver ${MAJOR_VERSIONS} )
 
+if( NOT ZDOOM_LIBS )
+	set( ZDOOM_LIBS "" )
+endif( NOT ZDOOM_LIBS )
+
 if( WIN32 )
 	if( X64 )
 		set( WIN_TYPE Win64 )
@@ -357,12 +375,16 @@ if( NOT NO_ASM )
 	endif( UNIX )
 	if( WIN32 )
 		set( FIXRTEXT fixrtext )
+	else( WIN32 )
+		set( FIXRTEXT "" )
 	endif( WIN32 )
 	message( STATUS "Selected assembler: ${ASSEMBLER}" )
 	MACRO( ADD_ASM_FILE indir infile )
 		set( ASM_OUTPUT_${infile} "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/zdoom.dir/${indir}/${infile}${ASM_OUTPUT_EXTENSION}" )
 		if( WIN32 )
 			set( FIXRTEXT_${infile} COMMAND ${FIXRTEXT} "${ASM_OUTPUT_${infile}}" )
+		else( WIN32 )
+			set( FIXRTEXT_${infile} COMMAND "" )
 		endif( WIN32 )
 		add_custom_command( OUTPUT ${ASM_OUTPUT_${infile}}
 			COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/zdoom.dir/${indir}
@@ -626,6 +648,9 @@ endif( WIN32 )
 if( NO_ASM )
 	add_definitions( -DNOASM )
 else( NO_ASM )
+	if( NOT ASM_SOURCES )
+		set( ASM_SOURCES "" )
+	endif( NOT ASM_SOURCES )
 	if( X64 )
 		ADD_ASM_FILE( asm_x86_64 tmap3 )
 	else( X64 )
diff --git a/tools/updaterevision/CMakeLists.txt b/tools/updaterevision/CMakeLists.txt
index b857ffbe72..2500f64fb7 100644
--- a/tools/updaterevision/CMakeLists.txt
+++ b/tools/updaterevision/CMakeLists.txt
@@ -15,6 +15,8 @@ if( WIN32 )
 			set( TRUSTINFO trustinfo.rc )
 		endif( MSVC_VERSION GREATER 1399 )
 	endif( "${CMAKE_C_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_C_COMPILER_ID}" STREQUAL "Clang" OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU" OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" )
+else( WIN32 )
+	set( TRUSTINFO "" )
 endif( WIN32 )
 
 if( NOT CMAKE_CROSSCOMPILING )