diff --git a/winpr/libwinpr/rpc/ndr_private.h b/winpr/libwinpr/rpc/ndr_private.h
index 357857e52..489d565c5 100644
--- a/winpr/libwinpr/rpc/ndr_private.h
+++ b/winpr/libwinpr/rpc/ndr_private.h
@@ -35,11 +35,11 @@ extern const NDR_TYPE_MARSHALL_ROUTINE pfnMarshallRoutines[];
 extern const NDR_TYPE_UNMARSHALL_ROUTINE pfnUnmarshallRoutines[];
 extern const NDR_TYPE_FREE_ROUTINE pfnFreeRoutines[];
 
-extern const char SimpleTypeAlignment[];
-extern const char SimpleTypeBufferSize[];
-extern const char SimpleTypeMemorySize[];
+extern const unsigned char SimpleTypeAlignment[];
+extern const unsigned char SimpleTypeBufferSize[];
+extern const unsigned char SimpleTypeMemorySize[];
 
-extern const char NdrTypeFlags[];
+extern const unsigned char NdrTypeFlags[];
 extern const char* FC_TYPE_STRINGS[];
 
 #include "ndr_correlation.h"
diff --git a/winpr/libwinpr/rpc/ndr_simple.c b/winpr/libwinpr/rpc/ndr_simple.c
index 46af05478..7fdff8c21 100644
--- a/winpr/libwinpr/rpc/ndr_simple.c
+++ b/winpr/libwinpr/rpc/ndr_simple.c
@@ -31,7 +31,7 @@
 #include "ndr_simple.h"
 #include "ndr_private.h"
 
-const char SimpleTypeAlignment[] =
+const unsigned char SimpleTypeAlignment[] =
 {
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01, 0x01, 0x03, 0x03, 0x03, 0x07, 0x07, 0x01, 0x03, 0x03,
 	0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -51,7 +51,7 @@ const char SimpleTypeAlignment[] =
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 };
 
-const char SimpleTypeBufferSize[] =
+const unsigned char SimpleTypeBufferSize[] =
 {
 	0x00, 0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x04, 0x04, 0x04, 0x08, 0x08, 0x02, 0x04, 0x04,
 	0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -71,7 +71,7 @@ const char SimpleTypeBufferSize[] =
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 };
 
-const char SimpleTypeMemorySize[] =
+const unsigned char SimpleTypeMemorySize[] =
 {
 	0x00, 0x01, 0x01, 0x01, 0x01, 0x02, 0x02, 0x02, 0x04, 0x04, 0x04, 0x08, 0x08, 0x04, 0x04, 0x04,
 	0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -91,7 +91,7 @@ const char SimpleTypeMemorySize[] =
 	0x92, 0x9D, 0x3A, 0x75, 0x92, 0x9D, 0x3A, 0x75, 0x92, 0x9D, 0x3A, 0x75, 0x92, 0x9D, 0x3A, 0x75,
 };
 
-const char NdrTypeFlags[] =
+const unsigned char NdrTypeFlags[] =
 {
 	0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
 	0x01, 0x02, 0x02, 0x02, 0x02, 0x84, 0x84, 0x84, 0x84, 0x84, 0x84, 0x08, 0x08, 0x08, 0x08, 0x08,
@@ -111,17 +111,17 @@ const char NdrTypeFlags[] =
 	0xAD, 0xAD, 0x9B, 0xBA, 0x9B, 0x9B, 0x0D, 0xB9, 0xAD, 0x19, 0x19, 0xBA, 0xDB, 0x09, 0x86, 0xB1,
 };
 
-char NdrGetSimpleTypeBufferAlignment(unsigned char FormatChar)
+unsigned char NdrGetSimpleTypeBufferAlignment(unsigned char FormatChar)
 {
 	return SimpleTypeAlignment[FormatChar];
 }
 
-char NdrGetSimpleTypeBufferSize(unsigned char FormatChar)
+unsigned char NdrGetSimpleTypeBufferSize(unsigned char FormatChar)
 {
 	return SimpleTypeAlignment[FormatChar];
 }
 
-char NdrGetSimpleTypeMemorySize(unsigned char FormatChar)
+unsigned char NdrGetSimpleTypeMemorySize(unsigned char FormatChar)
 {
 	return SimpleTypeMemorySize[FormatChar];
 }
@@ -131,7 +131,8 @@ int NdrGetTypeFlags(unsigned char FormatChar)
 	return NdrTypeFlags[FormatChar];
 }
 
-void NdrSimpleTypeBufferSize(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, PFORMAT_STRING pFormat)
+void NdrSimpleTypeBufferSize(PMIDL_STUB_MESSAGE pStubMsg,
+                             unsigned char* pMemory, PFORMAT_STRING pFormat)
 {
 	switch (*pFormat)
 	{
@@ -184,19 +185,19 @@ void NdrSimpleTypeBufferSize(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory
 	}
 }
 
-void NdrSimpleTypeMarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, unsigned char FormatChar)
+void NdrSimpleTypeMarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory,
+                           unsigned char FormatChar)
 {
-
 }
 
-void NdrSimpleTypeUnmarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, unsigned char FormatChar)
+void NdrSimpleTypeUnmarshall(PMIDL_STUB_MESSAGE pStubMsg,
+                             unsigned char* pMemory, unsigned char FormatChar)
 {
-
 }
 
-void NdrSimpleTypeFree(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, PFORMAT_STRING pFormat)
+void NdrSimpleTypeFree(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory,
+                       PFORMAT_STRING pFormat)
 {
-
 }
 
 #endif
diff --git a/winpr/libwinpr/rpc/ndr_simple.h b/winpr/libwinpr/rpc/ndr_simple.h
index 67e387a7d..ceb3ec655 100644
--- a/winpr/libwinpr/rpc/ndr_simple.h
+++ b/winpr/libwinpr/rpc/ndr_simple.h
@@ -24,14 +24,18 @@
 
 #ifndef _WIN32
 
-void NdrSimpleTypeBufferSize(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, PFORMAT_STRING pFormat);
-void NdrSimpleTypeMarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, unsigned char FormatChar);
-void NdrSimpleTypeUnmarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, unsigned char FormatChar);
-void NdrSimpleTypeFree(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory, PFORMAT_STRING pFormat);
+void NdrSimpleTypeBufferSize(PMIDL_STUB_MESSAGE pStubMsg,
+                             unsigned char* pMemory, PFORMAT_STRING pFormat);
+void NdrSimpleTypeMarshall(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory,
+                           unsigned char FormatChar);
+void NdrSimpleTypeUnmarshall(PMIDL_STUB_MESSAGE pStubMsg,
+                             unsigned char* pMemory, unsigned char FormatChar);
+void NdrSimpleTypeFree(PMIDL_STUB_MESSAGE pStubMsg, unsigned char* pMemory,
+                       PFORMAT_STRING pFormat);
 
-char NdrGetSimpleTypeBufferAlignment(unsigned char FormatChar);
-char NdrGetSimpleTypeBufferSize(unsigned char FormatChar);
-char NdrGetSimpleTypeMemorySize(unsigned char FormatChar);
+unsigned char NdrGetSimpleTypeBufferAlignment(unsigned char FormatChar);
+unsigned char NdrGetSimpleTypeBufferSize(unsigned char FormatChar);
+unsigned char NdrGetSimpleTypeMemorySize(unsigned char FormatChar);
 int NdrGetTypeFlags(unsigned char FormatChar);
 
 #endif