diff --git a/src/libpar2.h b/src/libpar2.h
index e99711fd..0366ed61 100644
--- a/src/libpar2.h
+++ b/src/libpar2.h
@@ -70,9 +70,13 @@ typedef signed long long   i64;
 #else // HAVE_CONFIG_H
 
 typedef   unsigned char        u8;
+typedef   signed char          i8;
 typedef   unsigned short       u16;
+typedef   signed short         i16;
 typedef   unsigned int         u32;
+typedef   signed int           i32;
 typedef   unsigned long long   u64;
+typedef   signed long long     i64;
 
 #endif
 #endif
diff --git a/src/par2cmdline.cpp b/src/par2cmdline.cpp
index 14a59f44..8d5fddca 100644
--- a/src/par2cmdline.cpp
+++ b/src/par2cmdline.cpp
@@ -56,10 +56,10 @@ int main(int argc, char* argv[])
 #endif
 
   // check sizeof integers
-  static_assert(sizeof(u8) == 1 || sizeof(i8) == 1
-		|| sizeof(u16) == 2 || sizeof(i16) == 1
-		|| sizeof(u32) == 4 || sizeof(i32) == 1
-		|| sizeof(u64) == 8 || sizeof(i64) == 1,
+  static_assert(sizeof(u8) == 1 && sizeof(i8) == 1
+		&& sizeof(u16) == 2 && sizeof(i16) == 2
+		&& sizeof(u32) == 4 && sizeof(i32) == 4
+		&& sizeof(u64) == 8 && sizeof(i64) == 8,
 		"Error: the assumed sizes of integers is wrong!");