diff --git a/configure.ac b/configure.ac
index 5eab08e..b49fbc5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -52,7 +52,9 @@ AC_PROG_LN_S
 AC_SUBST(SHELL)
 AC_SYS_LARGEFILE
 AC_FUNC_ALLOCA
-
+AC_PROG_CC_C99
+AS_IF([test "x$ac_cv_prog_cc_c99" = "xno"], 
+	AC_MSG_ERROR([C compiler does not support C99], 1))
 AC_CHECK_PROG([HAVE_POD2MAN], [pod2man], [yes])
 AS_IF([test "$HAVE_POD2MAN" != "yes"],
 	AC_MSG_FAILURE([pod2man is needed to generate manual from POD]))
diff --git a/lrzip.c b/lrzip.c
index 1820297..08ffe63 100644
--- a/lrzip.c
+++ b/lrzip.c
@@ -73,7 +73,7 @@ static i64 fdout_seekto(rzip_control *control, i64 pos)
 
 #ifdef __APPLE__
 # include <sys/sysctl.h>
-inline i64 get_ram(void)
+i64 get_ram(void)
 {
 	int mib[2];
 	size_t len;
@@ -89,7 +89,7 @@ inline i64 get_ram(void)
 	return ramsize;
 }
 #else /* __APPLE__ */
-inline i64 get_ram(rzip_control *control)
+i64 get_ram(rzip_control *control)
 {
 	i64 ramsize;
 	FILE *meminfo;
@@ -504,7 +504,7 @@ static bool open_tmpinbuf(rzip_control *control)
 	return true;
 }
 
-inline void clear_tmpinbuf(rzip_control *control)
+void clear_tmpinbuf(rzip_control *control)
 {
 	control->in_len = control->in_ofs = 0;
 }
diff --git a/lrzip.h b/lrzip.h
index d793776..b1631da 100644
--- a/lrzip.h
+++ b/lrzip.h
@@ -21,7 +21,7 @@
 
 #include "lrzip_private.h"
 
-inline i64 get_ram(rzip_control *control);
+i64 get_ram(rzip_control *control);
 i64 nloops(i64 seconds, uchar *b1, uchar *b2);
 bool write_magic(rzip_control *control);
 bool read_magic(rzip_control *control, int fd_in, i64 *expected_size);
@@ -39,7 +39,7 @@ bool write_fdin(rzip_control *control);
 bool flush_tmpoutbuf(rzip_control *control);
 void close_tmpoutbuf(rzip_control *control);
 void clear_tmpinbuf(rzip_control *control);
-inline bool clear_tmpinfile(rzip_control *control);
+bool clear_tmpinfile(rzip_control *control);
 void close_tmpinbuf(rzip_control *control);
 bool initialize_control(rzip_control *control);
 #endif