diff --git a/integration_test.py b/integration_test.py
index e5497db3..068da776 100644
--- a/integration_test.py
+++ b/integration_test.py
@@ -446,3 +446,38 @@ def test_incpath_dir(record_property, tmpdir):
 
     assert '' == stderr
     assert "error: could not open include 'inc'\n" == stdout
+
+
+def test_include_header_twice(tmpdir):
+    """ Issue #581 - Failure when header is included twice with different
+    macros defined"""
+
+    header_file = tmpdir / 'test.h'
+    with open(header_file, 'wt') as f:
+        f.write(f"""
+                #if defined AAA
+                #elif defined BBB
+                # undef BBB
+                #endif
+
+                #ifdef BBB
+                # error BBB is defined
+                #endif
+                """)
+
+    test_file = os.path.join(tmpdir, 'test.c')
+    with open(test_file, 'wt') as f:
+        f.write(f"""
+                # define Y
+                # include "test.h"
+
+                # define BBB
+                # include "test.h"
+                """)
+
+    args = [test_file]
+
+    _, stdout, stderr = simplecpp(args, cwd=tmpdir)
+
+    assert stderr == ''
+
diff --git a/simplecpp.cpp b/simplecpp.cpp
index 7d306fd7..ef891eb1 100644
--- a/simplecpp.cpp
+++ b/simplecpp.cpp
@@ -3701,12 +3701,11 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
                     else
                         ifstates.push(conditionIsTrue ? True : ElseIsTrue);
                     iftokens.push(rawtok);
-                } else if (ifstates.top() == True) {
-                    ifstates.top() = AlwaysFalse;
-                    iftokens.top()->nextcond = rawtok;
-                    iftokens.top() = rawtok;
-                } else if (ifstates.top() == ElseIsTrue && conditionIsTrue) {
-                    ifstates.top() = True;
+                } else {
+                    if (ifstates.top() == True)
+                        ifstates.top() = AlwaysFalse;
+                    else if (ifstates.top() == ElseIsTrue && conditionIsTrue)
+                        ifstates.top() = True;
                     iftokens.top()->nextcond = rawtok;
                     iftokens.top() = rawtok;
                 }