diff --git a/lib/dns/qp.c b/lib/dns/qp.c
index 3f10bd04a4..aa717c1301 100644
--- a/lib/dns/qp.c
+++ b/lib/dns/qp.c
@@ -495,10 +495,10 @@ static dns_qpcell_t
 next_capacity(uint32_t prev_capacity, uint32_t size) {
 	/*
 	 * Request size was floored at 2 because builtin_clz used to be 0.
-	 * We keep this behavior because ISC_LEADING_ZEROS(0) = 32.
+	 * We keep this behavior because stdc_leading_zeros(0) = 32.
 	 */
 	size = ISC_MAX3(size, prev_capacity, 2U);
-	uint32_t log2 = 32U - ISC_LEADING_ZEROS(size - 1U);
+	uint32_t log2 = 32U - stdc_leading_zeros(size - 1U);
 
 	return 1U << ISC_CLAMP(log2, QP_CHUNK_LOG_MIN, QP_CHUNK_LOG_MAX);
 }
diff --git a/lib/dns/qp_p.h b/lib/dns/qp_p.h
index a5dce44d84..ef9f1e3362 100644
--- a/lib/dns/qp_p.h
+++ b/lib/dns/qp_p.h
@@ -753,7 +753,7 @@ static inline dns_qpweight_t
 branch_count_bitmap_before(dns_qpnode_t *n, dns_qpshift_t bit) {
 	uint64_t mask = (1ULL << bit) - 1 - TAG_MASK;
 	uint64_t bitmap = branch_index(n) & mask;
-	return (dns_qpweight_t)ISC_POPCOUNT(bitmap);
+	return (dns_qpweight_t)stdc_count_zeros(bitmap);
 }
 
 /*
diff --git a/lib/dns/rpz.c b/lib/dns/rpz.c
index 3333478e20..8827a00c3c 100644
--- a/lib/dns/rpz.c
+++ b/lib/dns/rpz.c
@@ -1094,7 +1094,7 @@ diff_keys(const dns_rpz_cidr_key_t *key1, dns_rpz_prefix_t prefix1,
 	for (i = 0; bit < maxbit; i++, bit += DNS_RPZ_CIDR_WORD_BITS) {
 		delta = key1->w[i] ^ key2->w[i];
 		if (delta != 0) {
-			bit += ISC_LEADING_ZEROS(delta);
+			bit += stdc_leading_zeros(delta);
 			break;
 		}
 	}
diff --git a/lib/isc/histo.c b/lib/isc/histo.c
index 25febb55c9..aac7081db6 100644
--- a/lib/isc/histo.c
+++ b/lib/isc/histo.c
@@ -181,7 +181,7 @@ static inline uint
 value_to_key(const isc_histo_t *hg, uint64_t value) {
 	/* ensure that denormal numbers are all in chunk zero */
 	uint64_t chunked = value | CHUNKSIZE(hg);
-	int clz = ISC_LEADING_ZEROS(chunked);
+	int clz = stdc_leading_zeros(chunked);
 	/* actually 1 less than the exponent except for denormals */
 	uint exponent = 63 - hg->sigbits - clz;
 	/* mantissa has leading bit set except for denormals */
diff --git a/lib/isc/include/isc/bit.h b/lib/isc/include/isc/bit.h
index 2af9798bad..1f532be63d 100644
--- a/lib/isc/include/isc/bit.h
+++ b/lib/isc/include/isc/bit.h
@@ -19,26 +19,16 @@
 #include <isc/attributes.h>
 #include <isc/util.h>
 
-#ifndef __has_header
-#define __has_header(x) 0
-#endif
-
 #if __has_header(<stdbit.h>)
 
 #include <stdbit.h>
 
-#define ISC_POPCOUNT(x)	      stdc_count_zeros(x)
-#define ISC_LEADING_ZEROS(x)  stdc_leading_zeros(x)
-#define ISC_TRAILING_ZEROS(x) stdc_trailing_zeros(x)
-#define ISC_LEADING_ONES(x)   stdc_leading_ones(x)
-#define ISC_TRAILING_ONES(x)  stdc_trailing_ones(x)
-
 #else /* __has_header(<stdbit.h>) */
 
 #ifdef HAVE_BUILTIN_POPCOUNTG
-#define ISC_POPCOUNT(x) __builtin_popcountg(x)
+#define stdc_count_zeros(x) __builtin_popcountg(x)
 #else /* HAVE_BUILTIN_POPCOUNTG */
-#define ISC_POPCOUNT(x)                             \
+#define stdc_count_zeros(x)                         \
 	_Generic((x),                               \
 		unsigned int: __builtin_popcount,   \
 		unsigned long: __builtin_popcountl, \
@@ -46,9 +36,9 @@
 #endif /* HAVE_BUILTIN_POPCOUNTG */
 
 #ifdef HAVE_BUILTIN_CLZG
-#define ISC_LEADING_ZEROS(x) __builtin_clzg(x, (int)(sizeof(x) * 8))
+#define stdc_leading_zeros(x) __builtin_clzg(x, (int)(sizeof(x) * 8))
 #else /* HAVE_BUILTIN_CLZG */
-#define ISC_LEADING_ZEROS(x)                            \
+#define stdc_leading_zeros(x)                           \
 	(((x) == 0) ? (sizeof(x) * 8)                   \
 		    : _Generic((x),                     \
 			 unsigned int: __builtin_clz,   \
@@ -57,9 +47,9 @@
 #endif /* HAVE_BUILTIN_CLZG */
 
 #ifdef HAVE_BUILTIN_CTZG
-#define ISC_TRAILING_ZEROS(x) __builtin_ctzg(x, (int)sizeof(x) * 8)
+#define stdc_trailing_zeros(x) __builtin_ctzg(x, (int)sizeof(x) * 8)
 #else /* HAVE_BUILTIN_CTZG */
-#define ISC_TRAILING_ZEROS(x)                           \
+#define stdc_trailing_zeros(x)                          \
 	(((x) == 0) ? (sizeof(x) * 8)                   \
 		    : _Generic((x),                     \
 			 unsigned int: __builtin_ctz,   \
@@ -67,8 +57,8 @@
 			 unsigned long long: __builtin_ctzll)(x))
 #endif /* HAVE_BUILTIN_CTZG */
 
-#define ISC_LEADING_ONES(x)  ISC_LEADING_ZEROS(~(x))
-#define ISC_TRAILING_ONES(x) ISC_TRAILING_ZEROS(~(x))
+#define stdc_leading_ones(x)  stdc_leading_zeros(~(x))
+#define stdc_trailing_ones(x) stdc_trailing_zeros(~(x))
 
 #endif /* __has_header(<stdbit.h>) */
 
diff --git a/lib/isc/include/isc/util.h b/lib/isc/include/isc/util.h
index 971f21dc1e..95d93fd332 100644
--- a/lib/isc/include/isc/util.h
+++ b/lib/isc/include/isc/util.h
@@ -35,6 +35,10 @@
 #define __has_feature(x) 0
 #endif /* if !defined(__has_feature) */
 
+#ifndef __has_header
+#define __has_header(x) 0
+#endif
+
 /***
  *** General Macros.
  ***/