diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 5871cb668d0cb65906639a90596435ddedf9928f..16febb1ba7f0754ac7aa86da05ca0d66a983e45d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -1816,6 +1816,11 @@ iterative_hash_template_arg (tree arg, hashval_t val)
 	}
       return iterative_hash_template_arg (TREE_TYPE (arg), val);
 
+    case TEMPLATE_DECL:
+      if (DECL_TEMPLATE_TEMPLATE_PARM_P (arg))
+	return iterative_hash_template_arg (TREE_TYPE (arg), val);
+      break;
+
     case TARGET_EXPR:
       return iterative_hash_template_arg (TARGET_EXPR_INITIAL (arg), val);
 
@@ -4499,6 +4504,8 @@ struct ctp_hasher : ggc_ptr_hash<tree_node>
     hashval_t val = iterative_hash_object (code, 0);
     val = iterative_hash_object (TEMPLATE_TYPE_LEVEL (t), val);
     val = iterative_hash_object (TEMPLATE_TYPE_IDX (t), val);
+    if (TREE_CODE (t) == TEMPLATE_TYPE_PARM)
+      val = iterative_hash_template_arg (CLASS_PLACEHOLDER_TEMPLATE (t), val);
     if (TREE_CODE (t) == BOUND_TEMPLATE_TEMPLATE_PARM)
       val = iterative_hash_template_arg (TYPE_TI_ARGS (t), val);
     --comparing_specializations;
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index 77f57e0f9ac6f4c2244b2f2eb3e0d937e66eac75..5c8c05dc168be25cf91d1dbb75373c8276440fd8 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -4084,11 +4084,15 @@ cp_tree_equal (tree t1, tree t2)
 	}
       return false;
 
+    case TEMPLATE_DECL:
+      if (DECL_TEMPLATE_TEMPLATE_PARM_P (t1)
+	  && DECL_TEMPLATE_TEMPLATE_PARM_P (t2))
+	return cp_tree_equal (TREE_TYPE (t1), TREE_TYPE (t2));
+      /* Fall through.  */
     case VAR_DECL:
     case CONST_DECL:
     case FIELD_DECL:
     case FUNCTION_DECL:
-    case TEMPLATE_DECL:
     case IDENTIFIER_NODE:
     case SSA_NAME:
     case USING_DECL:
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 4937022ff20718ba68068b681a70e5e949adedd1..132c55cfc6d5693428a11a0812399303ebc64ebd 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -1573,8 +1573,8 @@ structural_comptypes (tree t1, tree t2, int strict)
 	return false;
       /* If T1 and T2 don't represent the same class template deduction,
          they aren't equal.  */
-      if (CLASS_PLACEHOLDER_TEMPLATE (t1)
-	  != CLASS_PLACEHOLDER_TEMPLATE (t2))
+      if (!cp_tree_equal (CLASS_PLACEHOLDER_TEMPLATE (t1),
+			  CLASS_PLACEHOLDER_TEMPLATE (t2)))
 	return false;
       /* Constrained 'auto's are distinct from parms that don't have the same
 	 constraints.  */
diff --git a/gcc/testsuite/g++.dg/template/ttp42.C b/gcc/testsuite/g++.dg/template/ttp42.C
new file mode 100644
index 0000000000000000000000000000000000000000..da08e857fc56d2ca903999cd3a62e1776d04583d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ttp42.C
@@ -0,0 +1,14 @@
+// PR c++/112737
+// { dg-do compile { target c++17 } }
+
+template<template<class> class TT>
+decltype(TT{42}) f(); // #1
+
+template<template<class> class TT>
+decltype(TT{42}) f(); // redeclaration of #1
+
+template<class T> struct A { A(T); };
+
+int main() {
+  f<A>();
+}
diff --git a/gcc/testsuite/g++.dg/template/ttp43.C b/gcc/testsuite/g++.dg/template/ttp43.C
new file mode 100644
index 0000000000000000000000000000000000000000..afafd321348d763969460a31998336d2a36e9bd6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/ttp43.C
@@ -0,0 +1,17 @@
+// PR c++/112737
+// { dg-do compile { target c++11 } }
+
+template<template<class> class, class T>
+void g(T);
+
+template<template<class> class TT, class T>
+decltype(g<TT>(T{})) f(T); // #1
+
+template<template<class> class TT, class T>
+decltype(g<TT>(T{})) f(T); // redeclaration of #1
+
+template<class T> struct A;
+
+int main() {
+  f<A>(0);
+}