diff --git a/Makefile.in b/Makefile.in
index f263fc32..ba6dd763 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -219,6 +219,7 @@ TESTS_UNIT := \
 	$(srcroot)test/unit/hook.c \
 	$(srcroot)test/unit/hpa.c \
 	$(srcroot)test/unit/hpa_central.c \
+	$(srcroot)test/unit/hpdata.c \
 	$(srcroot)test/unit/huge.c \
 	$(srcroot)test/unit/inspect.c \
 	$(srcroot)test/unit/junk.c \
diff --git a/include/jemalloc/internal/hpdata.h b/include/jemalloc/internal/hpdata.h
index cb034eae..e8433c53 100644
--- a/include/jemalloc/internal/hpdata.h
+++ b/include/jemalloc/internal/hpdata.h
@@ -112,10 +112,15 @@ hpdata_assert_empty(hpdata_t *hpdata) {
 	assert(hpdata_nfree_get(hpdata) == HUGEPAGE_PAGES);
 }
 
+static inline bool
+hpdata_consistent(hpdata_t *hpdata) {
+	return fb_urange_longest(hpdata->active_pages, HUGEPAGE_PAGES)
+	    == hpdata_longest_free_range_get(hpdata);
+}
+
 static inline void
 hpdata_assert_consistent(hpdata_t *hpdata) {
-	assert(fb_urange_longest(hpdata->active_pages, HUGEPAGE_PAGES)
-	    == hpdata_longest_free_range_get(hpdata));
+	assert(hpdata_consistent(hpdata));
 }
 
 TYPED_LIST(hpdata_list, hpdata_t, ql_link)
diff --git a/test/unit/hpdata.c b/test/unit/hpdata.c
new file mode 100644
index 00000000..1bf58bca
--- /dev/null
+++ b/test/unit/hpdata.c
@@ -0,0 +1,61 @@
+#include "test/jemalloc_test.h"
+
+#define HPDATA_ADDR ((void *)(10 * HUGEPAGE))
+#define HPDATA_AGE 123
+
+TEST_BEGIN(test_reserve_alloc) {
+	hpdata_t hpdata;
+	hpdata_init(&hpdata, HPDATA_ADDR, HPDATA_AGE);
+
+	/* Allocating a page at a time, we should do first fit. */
+	for (size_t i = 0; i < HUGEPAGE_PAGES; i++) {
+		expect_true(hpdata_consistent(&hpdata), "");
+		expect_zu_eq(HUGEPAGE_PAGES - i,
+		    hpdata_longest_free_range_get(&hpdata), "");
+		void *alloc = hpdata_reserve_alloc(&hpdata, PAGE);
+		expect_ptr_eq((char *)HPDATA_ADDR + i * PAGE, alloc, "");
+		expect_true(hpdata_consistent(&hpdata), "");
+	}
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(0, hpdata_longest_free_range_get(&hpdata), "");
+
+	/*
+	 * Build up a bigger free-range, 2 pages at a time, until we've got 6
+	 * adjacent free pages total.  Pages 8-13 should be unreserved after
+	 * this.
+	 */
+	hpdata_unreserve(&hpdata, (char *)HPDATA_ADDR + 10 * PAGE, 2 * PAGE);
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(2, hpdata_longest_free_range_get(&hpdata), "");
+
+	hpdata_unreserve(&hpdata, (char *)HPDATA_ADDR + 12 * PAGE, 2 * PAGE);
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(4, hpdata_longest_free_range_get(&hpdata), "");
+
+	hpdata_unreserve(&hpdata, (char *)HPDATA_ADDR + 8 * PAGE, 2 * PAGE);
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(6, hpdata_longest_free_range_get(&hpdata), "");
+
+	/*
+	 * Leave page 14 reserved, but free page 15 (this test the case where
+	 * unreserving combines two ranges).
+	 */
+	hpdata_unreserve(&hpdata, (char *)HPDATA_ADDR + 15 * PAGE, PAGE);
+	/*
+	 * Longest free range shouldn't change; we've got a free range of size
+	 * 6, then a reserved page, then another free range.
+	 */
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(6, hpdata_longest_free_range_get(&hpdata), "");
+
+	/* After freeing page 14, the two ranges get combined. */
+	hpdata_unreserve(&hpdata, (char *)HPDATA_ADDR + 14 * PAGE, PAGE);
+	expect_true(hpdata_consistent(&hpdata), "");
+	expect_zu_eq(8, hpdata_longest_free_range_get(&hpdata), "");
+}
+TEST_END
+
+int main(void) {
+	return test_no_reentrancy(
+	    test_reserve_alloc);
+}