diff --git a/internal/ceres/stringprintf.h b/internal/ceres/stringprintf.h
index f2f907a..cd1be14 100644
--- a/internal/ceres/stringprintf.h
+++ b/internal/ceres/stringprintf.h
@@ -65,17 +65,17 @@
 // Return a C++ string.
 extern string StringPrintf(const char* format, ...)
     // Tell the compiler to do printf format string checking.
-    CERES_PRINTF_ATTRIBUTE(1,2);
+    CERES_PRINTF_ATTRIBUTE(1, 2);
 
 // Store result into a supplied string and return it.
 extern const string& SStringPrintf(string* dst, const char* format, ...)
     // Tell the compiler to do printf format string checking.
-    CERES_PRINTF_ATTRIBUTE(2,3);
+    CERES_PRINTF_ATTRIBUTE(2, 3);
 
 // Append result to a supplied string.
 extern void StringAppendF(string* dst, const char* format, ...)
     // Tell the compiler to do printf format string checking.
-    CERES_PRINTF_ATTRIBUTE(2,3);
+    CERES_PRINTF_ATTRIBUTE(2, 3);
 
 // Lower-level routine that takes a va_list and appends to a specified string.
 // All other routines are just convenience wrappers around it.