diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
index 0ced0aaa..28b5fb78 100644
--- a/doc/jemalloc.xml.in
+++ b/doc/jemalloc.xml.in
@@ -941,7 +941,7 @@ for (i = 0; i < nbins; i++) {
       <varlistentry id="opt.narenas">
         <term>
           <mallctl>opt.narenas</mallctl>
-          (<type>size_t</type>)
+          (<type>unsigned</type>)
           <literal>r-</literal>
         </term>
         <listitem><para>Maximum number of arenas to use for automatic
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index 0260b9a8..a61a13a9 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -433,7 +433,7 @@ extern bool	opt_redzone;
 extern bool	opt_utrace;
 extern bool	opt_xmalloc;
 extern bool	opt_zero;
-extern size_t	opt_narenas;
+extern unsigned	opt_narenas;
 
 extern bool	in_valgrind;
 
diff --git a/src/ctl.c b/src/ctl.c
index a7f1b675..e0044336 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -1277,7 +1277,7 @@ CTL_RO_CONFIG_GEN(config_xmalloc, bool)
 CTL_RO_NL_GEN(opt_abort, opt_abort, bool)
 CTL_RO_NL_GEN(opt_dss, opt_dss, const char *)
 CTL_RO_NL_GEN(opt_lg_chunk, opt_lg_chunk, size_t)
-CTL_RO_NL_GEN(opt_narenas, opt_narenas, size_t)
+CTL_RO_NL_GEN(opt_narenas, opt_narenas, unsigned)
 CTL_RO_NL_GEN(opt_purge, purge_mode_names[opt_purge], const char *)
 CTL_RO_NL_GEN(opt_lg_dirty_mult, opt_lg_dirty_mult, ssize_t)
 CTL_RO_NL_GEN(opt_decay_time, opt_decay_time, ssize_t)
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 76b4f154..3d356c30 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -40,7 +40,7 @@ bool	opt_redzone = false;
 bool	opt_utrace = false;
 bool	opt_xmalloc = false;
 bool	opt_zero = false;
-size_t	opt_narenas = 0;
+unsigned	opt_narenas = 0;
 
 /* Initialized to true if the process is running inside Valgrind. */
 bool	in_valgrind;
@@ -1031,7 +1031,7 @@ malloc_conf_init(void)
 				if (cont)				\
 					continue;			\
 			}
-#define	CONF_HANDLE_SIZE_T(o, n, min, max, clip)			\
+#define	CONF_HANDLE_T_U(t, o, n, min, max, clip)			\
 			if (CONF_MATCH(n)) {				\
 				uintmax_t um;				\
 				char *end;				\
@@ -1045,11 +1045,11 @@ malloc_conf_init(void)
 					    k, klen, v, vlen);		\
 				} else if (clip) {			\
 					if ((min) != 0 && um < (min))	\
-						o = (min);		\
+						o = (t)(min);		\
 					else if (um > (max))		\
-						o = (max);		\
+						o = (t)(max);		\
 					else				\
-						o = um;			\
+						o = (t)um;		\
 				} else {				\
 					if (((min) != 0 && um < (min))	\
 					    || um > (max)) {		\
@@ -1058,10 +1058,14 @@ malloc_conf_init(void)
 						    "conf value",	\
 						    k, klen, v, vlen);	\
 					} else				\
-						o = um;			\
+						o = (t)um;		\
 				}					\
 				continue;				\
 			}
+#define	CONF_HANDLE_UNSIGNED(o, n, min, max, clip)			\
+			CONF_HANDLE_T_U(unsigned, o, n, min, max, clip)
+#define	CONF_HANDLE_SIZE_T(o, n, min, max, clip)			\
+			CONF_HANDLE_T_U(size_t, o, n, min, max, clip)
 #define	CONF_HANDLE_SSIZE_T(o, n, min, max)				\
 			if (CONF_MATCH(n)) {				\
 				long l;					\
@@ -1129,8 +1133,8 @@ malloc_conf_init(void)
 				}
 				continue;
 			}
-			CONF_HANDLE_SIZE_T(opt_narenas, "narenas", 1,
-			    SIZE_T_MAX, false)
+			CONF_HANDLE_UNSIGNED(opt_narenas, "narenas", 1,
+			    UINT_MAX, false)
 			if (strncmp("purge", k, klen) == 0) {
 				int i;
 				bool match = false;
diff --git a/src/stats.c b/src/stats.c
index 8d5ed71e..a7249479 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -435,9 +435,10 @@ stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		bool bv;
 		unsigned uv;
 		ssize_t ssv;
-		size_t sv, bsz, ssz, sssz, cpsz;
+		size_t sv, bsz, usz, ssz, sssz, cpsz;
 
 		bsz = sizeof(bool);
+		usz = sizeof(unsigned);
 		ssz = sizeof(size_t);
 		sssz = sizeof(ssize_t);
 		cpsz = sizeof(const char *);
@@ -464,6 +465,11 @@ stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 			    : "false", bv2 ? "true" : "false");		\
 		}							\
 }
+#define	OPT_WRITE_UNSIGNED(n)						\
+		if (je_mallctl("opt."#n, &uv, &usz, NULL, 0) == 0) {	\
+			malloc_cprintf(write_cb, cbopaque,		\
+			"  opt."#n": %zu\n", sv);			\
+		}
 #define	OPT_WRITE_SIZE_T(n)						\
 		if (je_mallctl("opt."#n, &sv, &ssz, NULL, 0) == 0) {	\
 			malloc_cprintf(write_cb, cbopaque,		\
@@ -494,7 +500,7 @@ stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		OPT_WRITE_BOOL(abort)
 		OPT_WRITE_SIZE_T(lg_chunk)
 		OPT_WRITE_CHAR_P(dss)
-		OPT_WRITE_SIZE_T(narenas)
+		OPT_WRITE_UNSIGNED(narenas)
 		OPT_WRITE_CHAR_P(purge)
 		if (opt_purge == purge_mode_ratio) {
 			OPT_WRITE_SSIZE_T_MUTABLE(lg_dirty_mult,
diff --git a/test/unit/mallctl.c b/test/unit/mallctl.c
index e8dc4926..01333514 100644
--- a/test/unit/mallctl.c
+++ b/test/unit/mallctl.c
@@ -163,7 +163,7 @@ TEST_BEGIN(test_mallctl_opt)
 	TEST_MALLCTL_OPT(bool, abort, always);
 	TEST_MALLCTL_OPT(size_t, lg_chunk, always);
 	TEST_MALLCTL_OPT(const char *, dss, always);
-	TEST_MALLCTL_OPT(size_t, narenas, always);
+	TEST_MALLCTL_OPT(unsigned, narenas, always);
 	TEST_MALLCTL_OPT(const char *, purge, always);
 	TEST_MALLCTL_OPT(ssize_t, lg_dirty_mult, always);
 	TEST_MALLCTL_OPT(ssize_t, decay_time, always);