diff --git a/common/jpeg/jpegint.h b/common/jpeg/jpegint.h
index 95b00d4..7a31f51 100644
--- a/common/jpeg/jpegint.h
+++ b/common/jpeg/jpegint.h
@@ -369,7 +369,7 @@
 
 /* Utility routines in jutils.c */
 EXTERN(long) jdiv_round_up JPP((long a, long b));
-EXTERN(long) jround_up JPP((long a, long b));
+EXTERN(size_t) jround_up JPP((size_t a, size_t b));
 EXTERN(void) jcopy_sample_rows JPP((JSAMPARRAY input_array, int source_row,
 				    JSAMPARRAY output_array, int dest_row,
 				    int num_rows, JDIMENSION num_cols));