diff --git a/reactos/tools/nci/ncitool.c b/reactos/tools/nci/ncitool.c
index d002a18c157..07838af1efa 100644
--- a/reactos/tools/nci/ncitool.c
+++ b/reactos/tools/nci/ncitool.c
@@ -103,7 +103,7 @@
                             "    ret $0x%x\n\n"
 
 #define KernelModeStub_amd64 "    movl $0x%x, %%eax\n" \
-                            "    call _KiSystemService\n" \
+                            "    call KiSystemService\n" \
                             "    ret $0x%x\n\n"
 
 /* For now, use the usermode stub.  We'll optimize later */
@@ -143,7 +143,7 @@ struct ncitool_data_t ncitool_data[] = {
     { "i386", 4, KernelModeStub_x86, UserModeStub_x86,
       ".global _%s@%d\n", "_%s@%d:\n" },
     { "amd64", 4, KernelModeStub_amd64, UserModeStub_amd64,
-      ".global _%s\n", "_%s:\n" },
+      ".global %s\n", "%s:\n" },
     { "powerpc", 4, KernelModeStub_ppc, UserModeStub_ppc,
       "\t.globl %s\n", "%s:\n" },
     { "mips", 4, KernelModeStub_mips, UserModeStub_mips,
diff --git a/reactos/tools/rsym/rsym64.h b/reactos/tools/rsym/rsym64.h
index 057fbb302bc..cae44f545b4 100644
--- a/reactos/tools/rsym/rsym64.h
+++ b/reactos/tools/rsym/rsym64.h
@@ -2,7 +2,13 @@
 
 //C_ASSERT(sizeof(ULONG) == 4);
 typedef unsigned char UBYTE;
+#if defined(_MSC_VER) || defined(__MINGW32__)
 typedef unsigned __int64 ULONG64;
+#else
+#include <stdint.h>
+typedef uint64_t ULONG64;
+#endif
+
 
 #define IMAGE_FILE_MACHINE_AMD64 0x8664
 #define IMAGE_DIRECTORY_ENTRY_IMPORT 1