diff --git a/Zend/configure.ac b/Zend/configure.ac
index 3ebea4b8ed1..5dfdccac6dd 100644
--- a/Zend/configure.ac
+++ b/Zend/configure.ac
@@ -68,7 +68,7 @@ int zend_sprintf(char *buffer, const char *format, ...);
 #elif defined(HAVE_FPCLASS)
 #define zend_isnan(a) ((fpclass(a) == FP_SNAN) || (fpclass(a) == FP_QNAN))
 #else
-#define zend_isnan(a) 0
+#define zend_isnan(a) ((a) != (a))
 #endif
 #endif
 
diff --git a/Zend/tests/bug73954.phpt b/Zend/tests/bug73954.phpt
new file mode 100644
index 00000000000..918f24b0f14
--- /dev/null
+++ b/Zend/tests/bug73954.phpt
@@ -0,0 +1,23 @@
+--TEST--
+Bug #73954 (NAN check fails on Alpine Linux with musl)
+--FILE--
+<?php
+
+var_dump(NAN);
+var_dump(is_nan(NAN));
+
+function takes_int(int $int) {
+}
+
+takes_int(NAN);
+
+?>
+--EXPECTF--
+float(NAN)
+bool(true)
+
+Fatal error: Uncaught TypeError: Argument 1 passed to takes_int() must be of the type integer, float given, called in %s on line 9 and defined in %s:6
+Stack trace:
+#0 %s(9): takes_int(NAN)
+#1 {main}
+  thrown in %s on line 6
diff --git a/configure.ac b/configure.ac
index dc7bff46eed..5584a4f43a3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -73,7 +73,7 @@ int zend_sprintf(char *buffer, const char *format, ...);
 #elif defined(HAVE_FPCLASS)
 #define zend_isnan(a) ((fpclass(a) == FP_SNAN) || (fpclass(a) == FP_QNAN))
 #else
-#define zend_isnan(a) 0
+#define zend_isnan(a) ((a) != (a))
 #endif
 #endif