diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 8c88e9061056..e761f701fe7d 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,11 @@
+2019-09-19  Ed Schonberg  <schonberg@adacore.com>
+
+	* sem_ch7.adb (Install_Parent_Private_Declarations): If a
+	generic child unit is instantiated within a sibling child unit,
+	the analysis of its private part requires that the private part
+	of the ancestor be available, as is done when the context
+	includes an instance of the ancestor.
+
 2019-09-19  Yannick Moy  <moy@adacore.com>
 
 	* inline.adb (Can_Be_Inlined_In_GNATprove_Mode): Add special
diff --git a/gcc/ada/sem_ch7.adb b/gcc/ada/sem_ch7.adb
index f7998c0d75bd..db6bffd96740 100644
--- a/gcc/ada/sem_ch7.adb
+++ b/gcc/ada/sem_ch7.adb
@@ -1508,9 +1508,21 @@ package body Sem_Ch7 is
                   Inst_Par := Renamed_Entity (Inst_Par);
                end if;
 
-               Gen_Par :=
-                 Generic_Parent
-                   (Specification (Unit_Declaration_Node (Inst_Par)));
+               --  The instance may appear in a sibling generic unit, in
+               --  which case the prefix must include the common (generic)
+               --  ancestor, which is treated as a current instance.
+
+               if Inside_A_Generic
+                 and then Ekind (Inst_Par) = E_Generic_Package
+               then
+                  Gen_Par := Inst_Par;
+                  pragma Assert (In_Open_Scopes (Gen_Par));
+
+               else
+                  Gen_Par :=
+                    Generic_Parent
+                      (Specification (Unit_Declaration_Node (Inst_Par)));
+               end if;
 
                --  Install the private declarations and private use clauses
                --  of a parent instance of the child instance, unless the
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index da23e2cd5af1..a3534f1442f7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-09-19  Ed Schonberg  <schonberg@adacore.com>
+
+	* gnat.dg/generic2-child.ads, gnat.dg/generic2-io_any.adb,
+	gnat.dg/generic2-io_any.ads, gnat.dg/generic2.ads: New testcase.
+
 2019-09-19  Yannick Moy  <moy@adacore.com>
 
 	* gnat.dg/global2.adb, gnat.dg/global2.ads: New testcase.
diff --git a/gcc/testsuite/gnat.dg/generic2-child.ads b/gcc/testsuite/gnat.dg/generic2-child.ads
new file mode 100644
index 000000000000..291cb23ecd83
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/generic2-child.ads
@@ -0,0 +1,5 @@
+generic
+package Generic2.Child is
+private
+  type My_Int is new Int;
+end Generic2.Child;
diff --git a/gcc/testsuite/gnat.dg/generic2-io_any.adb b/gcc/testsuite/gnat.dg/generic2-io_any.adb
new file mode 100644
index 000000000000..f077ad622cbd
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/generic2-io_any.adb
@@ -0,0 +1,5 @@
+--  { dg-do compile }
+
+package body Generic2.IO_Any is
+  procedure Dummy is null;
+end Generic2.IO_Any;
\ No newline at end of file
diff --git a/gcc/testsuite/gnat.dg/generic2-io_any.ads b/gcc/testsuite/gnat.dg/generic2-io_any.ads
new file mode 100644
index 000000000000..e56e229b114f
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/generic2-io_any.ads
@@ -0,0 +1,6 @@
+with Generic2.Child;
+generic
+package Generic2.IO_Any is
+  package V1 is new Generic2.Child;
+  procedure Dummy;
+end Generic2.IO_Any;
diff --git a/gcc/testsuite/gnat.dg/generic2.ads b/gcc/testsuite/gnat.dg/generic2.ads
new file mode 100644
index 000000000000..295d6b25c3c2
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/generic2.ads
@@ -0,0 +1,5 @@
+generic
+package Generic2 is
+private
+  type Int is new Integer;
+end Generic2;