diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index effa9642a90..a5b1dc6a144 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,17 @@
+2018-05-22  Olivier Hainque  <hainque@adacore.com>
+
+	* libgnat/a-except.adb (Exception_Propagation.Propagate_Exception):
+	Expect an Exception_Occurence object, not an Access.
+	(Complete_And_Propagate_Occurrence): Adjust accordingly.
+	(Raise_From_Signal_Handler): Likewise.
+	(Reraise_Occurrence_No_Defer): If we have a Machine_Occurrence
+	available in the provided occurrence object, just re-propagate the
+	latter as a bare "raise;" would do.
+	* libgnat/a-exexpr.adb (Propagate_Exception): Adjust to spec change.
+	* libgnat/a-exstat.adb (String_To_EO): Initialize X.Machine_Occurrence
+	to null, to mark that the occurrence we're crafting from the stream
+	contents is not being propagated (yet).
+
 2018-05-22  Hristian Kirtchev  <kirtchev@adacore.com>
 
 	* exp_aggr.adb (Initialize_Ctrl_Record_Component): Insert the generated
diff --git a/gcc/ada/libgnat/a-except.adb b/gcc/ada/libgnat/a-except.adb
index 0f45ace85df..c2f2f066979 100644
--- a/gcc/ada/libgnat/a-except.adb
+++ b/gcc/ada/libgnat/a-except.adb
@@ -228,7 +228,7 @@ package body Ada.Exceptions is
       function Allocate_Occurrence return EOA;
       --  Allocate an exception occurrence (as well as the machine occurrence)
 
-      procedure Propagate_Exception (Excep : EOA);
+      procedure Propagate_Exception (Excep : Exception_Occurrence);
       pragma No_Return (Propagate_Exception);
       --  This procedure propagates the exception represented by Excep
 
@@ -940,7 +940,7 @@ package body Ada.Exceptions is
    procedure Complete_And_Propagate_Occurrence (X : EOA) is
    begin
       Complete_Occurrence (X);
-      Exception_Propagation.Propagate_Exception (X);
+      Exception_Propagation.Propagate_Exception (X.all);
    end Complete_And_Propagate_Occurrence;
 
    ---------------------
@@ -1091,7 +1091,7 @@ package body Ada.Exceptions is
    is
    begin
       Exception_Propagation.Propagate_Exception
-        (Create_Occurrence_From_Signal_Handler (E, M));
+        (Create_Occurrence_From_Signal_Handler (E, M).all);
    end Raise_From_Signal_Handler;
 
    -------------------------
@@ -1587,12 +1587,25 @@ package body Ada.Exceptions is
    ---------------------------------
 
    procedure Reraise_Occurrence_No_Defer (X : Exception_Occurrence) is
-      Excep    : constant EOA := Exception_Propagation.Allocate_Occurrence;
-      Saved_MO : constant System.Address := Excep.Machine_Occurrence;
    begin
-      Save_Occurrence (Excep.all, X);
-      Excep.Machine_Occurrence := Saved_MO;
-      Complete_And_Propagate_Occurrence (Excep);
+      --  If we have a Machine_Occurrence at hand already, e.g. when we are
+      --  reraising a foreign exception, just repropagate. Otherwise, e.g.
+      --  when reraising a GNAT exception or an occurrence read back from a
+      --  stream, set up a new occurrence with its own Machine block first.
+
+      if X.Machine_Occurrence /= System.Null_Address then
+         Exception_Propagation.Propagate_Exception (X);
+      else
+         declare
+            Excep : constant EOA
+              := Exception_Propagation.Allocate_Occurrence;
+            Saved_MO : constant System.Address := Excep.Machine_Occurrence;
+         begin
+            Save_Occurrence (Excep.all, X);
+            Excep.Machine_Occurrence := Saved_MO;
+            Complete_And_Propagate_Occurrence (Excep);
+         end;
+      end if;
    end Reraise_Occurrence_No_Defer;
 
    ---------------------
diff --git a/gcc/ada/libgnat/a-exexpr.adb b/gcc/ada/libgnat/a-exexpr.adb
index 465add96161..2fe003ef011 100644
--- a/gcc/ada/libgnat/a-exexpr.adb
+++ b/gcc/ada/libgnat/a-exexpr.adb
@@ -349,7 +349,7 @@ package body Exception_Propagation is
    -- Propagate_Exception --
    -------------------------
 
-   procedure Propagate_Exception (Excep : EOA) is
+   procedure Propagate_Exception (Excep : Exception_Occurrence) is
    begin
       Propagate_GCC_Exception (To_GCC_Exception (Excep.Machine_Occurrence));
    end Propagate_Exception;
diff --git a/gcc/ada/libgnat/a-exstat.adb b/gcc/ada/libgnat/a-exstat.adb
index 8943939ff4f..166cbb19f7f 100644
--- a/gcc/ada/libgnat/a-exstat.adb
+++ b/gcc/ada/libgnat/a-exstat.adb
@@ -256,6 +256,11 @@ package body Stream_Attributes is
          end loop;
       end if;
 
+      --  The occurrence we're crafting is not currently being
+      --  propagated.
+
+      X.Machine_Occurrence := System.Null_Address;
+
       --  If an exception was converted to a string, it must have
       --  already been raised, so flag it accordingly and we are done.