diff --git a/dmd2/mars.c b/dmd2/mars.c
index 9ccf07d7..d04b7024 100644
--- a/dmd2/mars.c
+++ b/dmd2/mars.c
@@ -72,9 +72,7 @@ Global::Global()
     bc_ext  = "bc";
     s_ext   = "s";
     obj_ext = "o";
-#if _WIN32
     obj_ext_alt = "obj";
-#endif
 #else
 #if TARGET_WINDOS
     obj_ext  = "obj";
diff --git a/dmd2/mars.h b/dmd2/mars.h
index 36dc7b51..9d56203e 100644
--- a/dmd2/mars.h
+++ b/dmd2/mars.h
@@ -285,12 +285,10 @@ struct Global
     const char *sym_ext;
     const char *obj_ext;
 #if IN_LLVM
-#if _WIN32
-    char *obj_ext_alt;
-#endif
-    char *ll_ext;
-    char *bc_ext;
-    char *s_ext;
+    const char *obj_ext_alt;
+    const char *ll_ext;
+    const char *bc_ext;
+    const char *s_ext;
 #endif
     const char *lib_ext;
     const char *dll_ext;
diff --git a/dmd2/module.c b/dmd2/module.c
index bd381808..1a98b4f0 100644
--- a/dmd2/module.c
+++ b/dmd2/module.c
@@ -358,10 +358,10 @@ void Module::buildTargetFiles(bool singleObj)
 	if(!objfile)
 	{
 		if (global.params.output_o)
-			objfile = Module::buildFilePath(global.params.objname, global.params.objdir, global.obj_ext);
+			objfile = Module::buildFilePath(global.params.objname, global.params.objdir, global.params.os == OSWindows ? global.obj_ext_alt : global.obj_ext);
 		else if (global.params.output_bc)
 			objfile = Module::buildFilePath(global.params.objname, global.params.objdir, global.bc_ext);
-		else if (global.params.output_ll)
+		else if (global.params.output_ll) 
 			objfile = Module::buildFilePath(global.params.objname, global.params.objdir, global.ll_ext);
 		else if (global.params.output_s)
 			objfile = Module::buildFilePath(global.params.objname, global.params.objdir, global.s_ext);
diff --git a/driver/main.cpp b/driver/main.cpp
index f768e7df..e188cdf1 100644
--- a/driver/main.cpp
+++ b/driver/main.cpp
@@ -391,17 +391,16 @@ int main(int argc, char** argv)
         } else if (strcmp(ext, global.s_ext) == 0) {
             global.params.output_s = OUTPUTFLAGset;
             autofound = true;
-        } else if (strcmp(ext, global.obj_ext) == 0) {
+        } else if (strcmp(ext, global.obj_ext) == 0 || strcmp(ext, global.obj_ext_alt) == 0) {
             global.params.output_o = OUTPUTFLAGset;
             autofound = true;
         } else {
             // append dot, so forceExt won't change existing name even if it contains dots
             size_t len = strlen(global.params.objname);
-            size_t extlen = strlen(".");
-            char* s = static_cast<char *>(mem.malloc(len + 1 + extlen + 1));
+            char* s = static_cast<char *>(mem.malloc(len + 1 + 1));
             memcpy(s, global.params.objname, len);
             s[len] = '.';
-            s[len+1+extlen] = 0;
+            s[len+1] = 0;
             global.params.objname = s;
 
         }
diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 3c36a1f8..10803e52 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -187,7 +187,7 @@ macro(dc INPUT_D OUTLIST_O OUTLIST_BC MOREFLAGS PATH SUFFIX)
     else ("${path}" STREQUAL "")
         set(output ${path}/${name})
     endif ("${path}" STREQUAL "")
-    set(OUTPUT_O ${PROJECT_BINARY_DIR}/${output}${SUFFIX}.o)
+    set(OUTPUT_O ${PROJECT_BINARY_DIR}/${output}${SUFFIX}${CMAKE_C_OUTPUT_EXTENSION})
     set(OUTPUT_BC ${PROJECT_BINARY_DIR}/${output}${SUFFIX}.bc)
     list(APPEND ${OUTLIST_O} ${OUTPUT_O})
     list(APPEND ${OUTLIST_BC} ${OUTPUT_BC})