diff --git a/lib/gnat/aunit.gpr b/lib/gnat/aunit.gpr
index 7bb2a67..f11a8b1 100644
--- a/lib/gnat/aunit.gpr
+++ b/lib/gnat/aunit.gpr
@@ -24,6 +24,8 @@ project AUnit is
          for Library_Kind use "dynamic";
          for Library_Version use "lib" & project'Library_name & ".so."
            & AUnit_Shared.Soversion;
+         --  Put options like --as-needed before the libraries.
+         for Leading_Library_Options use AUnit_Shared.Ldflags;
    end case;
 
    for Library_Dir use "../aunit/"
@@ -51,6 +53,9 @@ project AUnit is
             for Default_Switches ("ada") use
               ("-O2", "-gnatp", "-gnatn", "-gnatwa.X");
       end case;
+      --  Allow user flags to override default flags.
+      for Default_Switches ("ada") use Compiler'Default_Switches ("ada")
+        & AUnit_Shared.Adaflags;
 
       for Switches ("aunit.adb") use
         Compiler'Default_Switches ("ada") & ("-fno-strict-aliasing");
diff --git a/lib/gnat/aunit_shared.gpr b/lib/gnat/aunit_shared.gpr
index d3ee1ff..1e1fddb 100644
--- a/lib/gnat/aunit_shared.gpr
+++ b/lib/gnat/aunit_shared.gpr
@@ -18,6 +18,9 @@ project AUnit_Shared is
    --  A non-empty soversion requires a shared library.
    Soversion := External ("aunit_SOVERSION", "");
 
+   Adaflags  := External_As_List ("ADAFLAGS", " ");
+   Ldflags   := External_As_List ("LDFLAGS",  " ");
+
    for Source_Dirs use ();
 
    type Exception_Type is ("fullexception", "certexception", "zfpexception");