diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -45,6 +45,7 @@
 #include "clang/Sema/Template.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/Support/Casting.h"
 #include <algorithm>
 #include <cstring>
 #include <functional>
@@ -14345,7 +14346,16 @@
       ActivePolicy = &WP;
     }
 
+    bool ErrorsInCtorInitializer =
+        llvm::isa_and_nonnull<CXXConstructorDecl>(FD)
+            ? llvm::any_of(llvm::dyn_cast<CXXConstructorDecl>(FD)->inits(),
+                           [](const auto *Init) {
+                             return Init->getInit() &&
+                                    Init->getInit()->containsErrors();
+                           })
+            : false;
     if (!IsInstantiation && FD && FD->isConstexpr() && !FD->isInvalidDecl() &&
+        !ErrorsInCtorInitializer &&
         !CheckConstexprFunctionDefinition(FD, CheckConstexprKind::Diagnose))
       FD->setInvalidDecl();
 
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1685,6 +1685,7 @@
 // This implements C++11 [dcl.constexpr]p3,4, as amended by DR1360.
 bool Sema::CheckConstexprFunctionDefinition(const FunctionDecl *NewFD,
                                             CheckConstexprKind Kind) {
+  assert(!NewFD->isInvalidDecl());
   const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
   if (MD && MD->isInstance()) {
     // C++11 [dcl.constexpr]p4:
diff --git a/clang/test/SemaCXX/invalid-constructor-init.cpp b/clang/test/SemaCXX/invalid-constructor-init.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/SemaCXX/invalid-constructor-init.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -frecovery-ast -verify %s
+
+struct X {
+  int Y;
+  constexpr X() : Y(foo()) {} // expected-error {{use of undeclared identifier 'foo'}}
+};
+
+struct X2 {
+  int Y = foo(); // expected-error {{use of undeclared identifier 'foo'}} \
+                 // expected-note {{subexpression not valid in a constant expression}}
+  constexpr X2() {} // expected-error {{constexpr constructor never produces a constant expression}}
+};
+
+struct CycleDelegate {
+  int Y;
+  CycleDelegate(int) : Y(foo()) {} // expected-error {{use of undeclared identifier 'foo'}}
+  // no "delegation cycle" diagnostic emitted!
+  CycleDelegate(float) : CycleDelegate(1) {}
+};