diff --git a/Misc/NEWS b/Misc/NEWS
index c06539bdfdc..efa0f76229b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -167,6 +167,10 @@ Tests
 - Issue #27369: In test_pyexpat, avoid testing an error message detail that
   changed in Expat 2.2.0.
 
+- Issue #27594: Prevent assertion error when running test_ast with coverage
+  enabled: ensure code object has a valid first line number.
+  Patch suggested by Ivan Levkivskyi.
+
 Windows
 -------
 
diff --git a/Python/compile.c b/Python/compile.c
index e46676c0b03..fb80f51fc00 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -4963,7 +4963,7 @@ assemble(struct compiler *c, int addNone)
 
     /* Set firstlineno if it wasn't explicitly set. */
     if (!c->u->u_firstlineno) {
-        if (entryblock && entryblock->b_instr)
+        if (entryblock && entryblock->b_instr && entryblock->b_instr->i_lineno)
             c->u->u_firstlineno = entryblock->b_instr->i_lineno;
         else
             c->u->u_firstlineno = 1;