Index: src/amiga-library.h
==================================================================
--- src/amiga-library.h
+++ src/amiga-library.h
@@ -69,12 +69,17 @@
 	void (*_Nonnull __deregister_frame)(void *_Nonnull);
 #endif
 	int *_Nonnull (*_Nonnull errNo)(void);
 
 	/* Needed only by ObjFW. */
+#ifdef OF_MORPHOS
+	int (*_Nonnull vasprintf)(char *_Nonnull *_Nullable restrict,
+	    const char *_Nonnull restrict, va_list);
+#else
 	int (*_Nonnull vsnprintf)(char *_Nonnull restrict, size_t,
 	    const char *_Nonnull restrict, va_list);
+#endif
 	float (*_Nonnull strtof)(const char *_Nonnull,
 	    char *_Nullable *_Nullable);
 	double (*_Nonnull strtod)(const char *_Nonnull,
 	    char *_Nullable *_Nullable);
 #ifdef OF_MORPHOS

Index: src/amiga-library.m
==================================================================
--- src/amiga-library.m
+++ src/amiga-library.m
@@ -526,16 +526,37 @@
 OFErrNo(void)
 {
 	return libC.errNo();
 }
 
+#ifdef OF_MORPHOS
+int
+vasprintf(char **restrict strp, const char *restrict fmt, va_list args)
+{
+	return libC.vasprintf(strp, fmt, args);
+}
+
+int
+asprintf(char **restrict strp, const char *restrict fmt, ...)
+{
+	va_list args;
+	int ret;
+
+	va_start(args, fmt);
+	ret = vasprintf(strp, fmt, args);
+	va_end(args);
+
+	return ret;
+}
+#else
 int
 vsnprintf(char *restrict str, size_t size, const char *restrict fmt,
     va_list args)
 {
 	return libC.vsnprintf(str, size, fmt, args);
 }
+#endif
 
 float
 strtof(const char *str, char **endptr)
 {
 	return libC.strtof(str, endptr);

Index: src/linklib/init.m
==================================================================
--- src/linklib/init.m
+++ src/linklib/init.m
@@ -340,11 +340,15 @@
 #ifdef OF_MORPHOS
 		.__register_frame = __register_frame,
 		.__deregister_frame = __deregister_frame,
 #endif
 		.errNo = errNo,
+#ifdef OF_MORPHOS
+		.vasprintf = vasprintf,
+#else
 		.vsnprintf = vsnprintf,
+#endif
 		.strtof = strtof,
 		.strtod = strtod,
 #ifdef OF_MORPHOS
 		.gmtime_r = gmtime_r,
 		.localtime_r = localtime_r,