diff --git a/error.c b/error.c
index 32409e1e41..70ba070f42 100644
--- a/error.c
+++ b/error.c
@@ -2321,7 +2321,7 @@ name_err_mesg_to_str(VALUE obj)
     VALUE mesg = ptr->mesg;
     if (NIL_P(mesg)) return Qnil;
     else {
-        struct RString s_str, c_str, d_str;
+        struct RString s_str = {RBASIC_INIT}, c_str = {RBASIC_INIT}, d_str = {RBASIC_INIT};
         VALUE c, s, d = 0, args[4], c2;
         int state = 0;
         rb_encoding *usascii = rb_usascii_encoding();
diff --git a/ext/-test-/string/fstring.c b/ext/-test-/string/fstring.c
index 8dfa36e345..8d037028a9 100644
--- a/ext/-test-/string/fstring.c
+++ b/ext/-test-/string/fstring.c
@@ -14,7 +14,7 @@ VALUE
 bug_s_fstring_fake_str(VALUE self)
 {
     static const char literal[] = "abcdefghijklmnopqrstuvwxyz";
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return rb_fstring(rb_setup_fake_str(&fake_str, literal, sizeof(literal) - 1, 0));
 }
 
diff --git a/include/ruby/internal/attr/nonstring.h b/include/ruby/internal/attr/nonstring.h
index de26e926d4..5ad6ef2a86 100644
--- a/include/ruby/internal/attr/nonstring.h
+++ b/include/ruby/internal/attr/nonstring.h
@@ -25,8 +25,16 @@
 /** Wraps (or simulates) `__attribute__((nonstring))` */
 #if RBIMPL_HAS_ATTRIBUTE(nonstring)
 # define RBIMPL_ATTR_NONSTRING() __attribute__((nonstring))
+# if RBIMPL_COMPILER_SINCE(GCC, 15, 0, 0)
+#   define RBIMPL_ATTR_NONSTRING_ARRAY() RBIMPL_ATTR_NONSTRING()
+# elif RBIMPL_COMPILER_SINCE(Clang, 21, 0, 0)
+#   define RBIMPL_ATTR_NONSTRING_ARRAY() RBIMPL_ATTR_NONSTRING()
+# else
+#   define RBIMPL_ATTR_NONSTRING_ARRAY() /* void */
+# endif
 #else
 # define RBIMPL_ATTR_NONSTRING() /* void */
+# define RBIMPL_ATTR_NONSTRING_ARRAY() /* void */
 #endif
 
 #endif /* RBIMPL_ATTR_NONSTRING_H */
diff --git a/include/ruby/internal/core/rbasic.h b/include/ruby/internal/core/rbasic.h
index 4617f743a7..c63968ce13 100644
--- a/include/ruby/internal/core/rbasic.h
+++ b/include/ruby/internal/core/rbasic.h
@@ -104,6 +104,9 @@ RBasic {
         klass(RBIMPL_VALUE_NULL)
     {
     }
+# define RBASIC_INIT RBasic()
+#else
+# define RBASIC_INIT {RBIMPL_VALUE_NULL}
 #endif
 };
 
diff --git a/include/ruby/internal/core/rstring.h b/include/ruby/internal/core/rstring.h
index 0bca74e688..9cf9daa97c 100644
--- a/include/ruby/internal/core/rstring.h
+++ b/include/ruby/internal/core/rstring.h
@@ -395,7 +395,7 @@ rbimpl_rstring_getmem(VALUE str)
     }
     else {
         /* Expecting compilers to optimize this on-stack struct away. */
-        struct RString retval;
+        struct RString retval = {RBASIC_INIT};
         retval.len = RSTRING_LEN(str);
         retval.as.heap.ptr = RSTRING(str)->as.embed.ary;
         return retval;
diff --git a/load.c b/load.c
index 6716f6d973..81da211f5d 100644
--- a/load.c
+++ b/load.c
@@ -1368,7 +1368,7 @@ rb_require_internal(VALUE fname)
 int
 ruby_require_internal(const char *fname, unsigned int len)
 {
-    struct RString fake;
+    struct RString fake = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake, fname, len, 0);
     rb_execution_context_t *ec = GET_EC();
     int result = require_internal(ec, str, 0, RTEST(ruby_verbose));
@@ -1402,7 +1402,7 @@ rb_require_string_internal(VALUE fname, bool resurrect)
 VALUE
 rb_require(const char *fname)
 {
-    struct RString fake;
+    struct RString fake = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake, fname, strlen(fname), 0);
     return rb_require_string_internal(str, true);
 }
diff --git a/marshal.c b/marshal.c
index 3ef3ef3636..5ec2f5f041 100644
--- a/marshal.c
+++ b/marshal.c
@@ -1438,7 +1438,7 @@ long
 ruby_marshal_read_long(const char **buf, long len)
 {
     long x;
-    struct RString src;
+    struct RString src = {RBASIC_INIT};
     struct load_arg arg;
     memset(&arg, 0, sizeof(arg));
     arg.src = rb_setup_fake_str(&src, *buf, len, 0);
diff --git a/string.c b/string.c
index 41cdfe0c65..44734c695e 100644
--- a/string.c
+++ b/string.c
@@ -486,14 +486,14 @@ rb_setup_fake_str(struct RString *fake_str, const char *name, long len, rb_encod
 VALUE
 rb_fstring_new(const char *ptr, long len)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(setup_fake_str(&fake_str, ptr, len, ENCINDEX_US_ASCII), FALSE);
 }
 
 VALUE
 rb_fstring_enc_new(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(rb_setup_fake_str(&fake_str, ptr, len, enc), FALSE);
 }
 
@@ -12084,7 +12084,7 @@ rb_str_to_interned_str(VALUE str)
 VALUE
 rb_interned_str(const char *ptr, long len)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(setup_fake_str(&fake_str, ptr, len, ENCINDEX_US_ASCII), TRUE);
 }
 
@@ -12101,7 +12101,7 @@ rb_enc_interned_str(const char *ptr, long len, rb_encoding *enc)
         rb_enc_autoload(enc);
     }
 
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     return register_fstring(rb_setup_fake_str(&fake_str, ptr, len, enc), TRUE);
 }
 
diff --git a/symbol.c b/symbol.c
index 325afccfe0..03ca9cf150 100644
--- a/symbol.c
+++ b/symbol.c
@@ -736,7 +736,7 @@ ID
 rb_intern3(const char *name, long len, rb_encoding *enc)
 {
     VALUE sym;
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     VALUE str = rb_setup_fake_str(&fake_str, name, len, enc);
     OBJ_FREEZE(str);
     sym = lookup_str_sym(str);
@@ -1191,7 +1191,7 @@ rb_check_symbol(volatile VALUE *namep)
 ID
 rb_check_id_cstr(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
 
     sym_check_asciionly(name, true);
@@ -1203,7 +1203,7 @@ VALUE
 rb_check_symbol_cstr(const char *ptr, long len, rb_encoding *enc)
 {
     VALUE sym;
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
 
     sym_check_asciionly(name, true);
@@ -1227,7 +1227,7 @@ FUNC_MINIMIZED(VALUE rb_sym_intern_ascii_cstr(const char *ptr));
 VALUE
 rb_sym_intern(const char *ptr, long len, rb_encoding *enc)
 {
-    struct RString fake_str;
+    struct RString fake_str = {RBASIC_INIT};
     const VALUE name = rb_setup_fake_str(&fake_str, ptr, len, enc);
     return rb_str_intern(name);
 }
diff --git a/version.h b/version.h
index 33fa2ca6c4..b1ed91dc9c 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 9
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 177
+#define RUBY_PATCHLEVEL 178
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"