diff --git a/.gdbinit b/.gdbinit
index 9281744c137..5ce089d3c40 100644
--- a/.gdbinit
+++ b/.gdbinit
@@ -972,10 +972,31 @@ document rb_ps_vm
 Dump all threads in a (rb_vm_t*) and their callstacks
 end
 
+# CFP_ISEQ() and CFP_PC() in zjit.h, written without calling a function so
+# that they work on a core file too. Sets $iseq and $cfp_pc.
+define cfp_iseq_pc
+  set $iseq = $arg0->_iseq
+  set $cfp_pc = $arg0->pc
+  python gdb.set_convenience_variable('zjit_built', gdb.lookup_global_symbol('rb_zjit_entry') is not None)
+  if $zjit_built
+    if rb_zjit_entry && $arg0->jit_return
+      if (VALUE)$arg0->jit_return == 1
+        # ZJIT_JIT_RETURN_C_FRAME
+        set $iseq = 0
+        set $cfp_pc = 0
+      else
+        set $jit_frame = ((zjit_jit_frame_t **)$arg0->jit_return)[-1]
+        set $iseq = $jit_frame->iseq
+        set $cfp_pc = $jit_frame->pc
+      end
+    end
+  end
+end
+
 define print_lineno
   set $cfp = $arg0
-  set $iseq = rb_get_cfp_iseq($cfp)
-  set $pos = $cfp->pc - $iseq->body->iseq_encoded
+  cfp_iseq_pc $cfp
+  set $pos = $cfp_pc - $iseq->body->iseq_encoded
   if $pos != 0
     set $pos = $pos - 1
   end
@@ -1098,8 +1119,8 @@ define rb_ps_thread
   set $cfp = $ps_thread_th->ec->cfp
   set $cfpend = (rb_control_frame_t *)($ps_thread_th->ec->vm_stack + $ps_thread_th->ec->vm_stack_size)-1
   while $cfp < $cfpend
-    if $cfp->_iseq
-      set $iseq = rb_get_cfp_iseq($cfp)
+    cfp_iseq_pc $cfp
+    if $iseq
       if !((VALUE)$iseq & RUBY_IMMEDIATE_MASK) && (((imemo_ifunc << RUBY_FL_USHIFT) | RUBY_T_IMEMO)==$iseq->flags & (RUBY_IMEMO_MASK | RUBY_T_MASK))
         printf "%d:ifunc ", $cfpend-$cfp
         set print symbol-filename on
@@ -1107,7 +1128,7 @@ define rb_ps_thread
         set print symbol-filename off
         printf "\n"
       else
-      if $cfp->pc
+      if $cfp_pc
         set $location = $iseq->body->location
         printf "%d:", $cfpend-$cfp
         print_pathobj $location.pathobj