diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index da93c95d39..d91bdd6737 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -291,7 +291,11 @@ jobs:
             container: 'alpine:3.20'
 
           - name: Alpine MUSL c-ares https-rr
-            configure: --enable-debug --with-ssl --with-libssh2 --with-libidn2 --with-gssapi --enable-ldap --with-libpsl --disable-threaded-resolver --enable-ares --enable-httpsrr --disable-unity
+            configure: --enable-debug --with-ssl --with-libssh2 --with-libidn2 --with-gssapi --enable-ldap --with-libpsl --disable-threaded-resolver --enable-ares --enable-httpsrr --disable-werror
+            container: 'alpine:3.20'
+
+          - name: Alpine MUSL c-ares https-rr !debug
+            configure: --enable-debug --with-ssl --with-libssh2 --with-libidn2 --with-gssapi --enable-ldap --with-libpsl --disable-threaded-resolver --enable-ares --enable-httpsrr --disable-werror --disable-debug
             container: 'alpine:3.20'
 
     steps:
diff --git a/CMake/unix-cache.cmake b/CMake/unix-cache.cmake
index e0e1d8f947..6ccd7b8377 100644
--- a/CMake/unix-cache.cmake
+++ b/CMake/unix-cache.cmake
@@ -309,3 +309,11 @@ if(CYGWIN)
 endif()
 set(STDC_HEADERS 1)
 set(USE_UNIX_SOCKETS 1)
+
+if(MUSL)
+  set(HAVE_GLIBC_STRERROR_R 0)
+  set(HAVE_LINUX_TCP_H 0)
+  set(HAVE_POSIX_STRERROR_R 1)
+  set(HAVE_STROPTS_H 1)
+  set(HAVE_TERMIOS_H 0)
+endif()
diff --git a/lib/easy_lock.h b/lib/easy_lock.h
index ec324cfc81..a61df8365a 100644
--- a/lib/easy_lock.h
+++ b/lib/easy_lock.h
@@ -45,6 +45,12 @@
 #elif defined(HAVE_ATOMIC) && defined(HAVE_STDATOMIC_H)
 #include <stdatomic.h>
 #if defined(HAVE_SCHED_YIELD)
+/* Hack for Unity mode. Avoid macro collisions with MUSL 1.25 and older */
+#ifdef HEADER_CURL_MEMDEBUG_H
+#undef HEADER_CURL_MEMDEBUG_H
+#undef calloc
+#undef free
+#endif
 #include <sched.h>
 #endif
 
diff --git a/lib/memdebug.h b/lib/memdebug.h
index f45d4925f6..8bb7df4fd2 100644
--- a/lib/memdebug.h
+++ b/lib/memdebug.h
@@ -33,6 +33,11 @@
 #include <curl/curl.h>
 #include "functypes.h"
 
+/* Avoid double definitions/declarations, in case we include this header
+   again after a 'memdebug_reset.h'. */
+#ifndef HEADER_CURL_MEMDEBUG_H_DECL
+#define HEADER_CURL_MEMDEBUG_H_DECL
+
 #if defined(__GNUC__) && __GNUC__ >= 3
 #  define ALLOC_FUNC __attribute__((__malloc__))
 #  define ALLOC_SIZE(s) __attribute__((__alloc_size__(s)))
@@ -108,6 +113,7 @@ CURL_EXTERN ALLOC_FUNC FILE *curl_dbg_fdopen(int filedes, const char *mode,
                                              int line, const char *source);
 
 CURL_EXTERN int curl_dbg_fclose(FILE *file, int line, const char *source);
+#endif /* HEADER_CURL_MEMDEBUG_H_DECL */
 
 #ifndef MEMDEBUG_NODEFINES