diff --git a/modules/spin-tools/src-tests/com/maccasoft/propeller/PreferencesTest.java b/modules/spin-tools/src-tests/com/maccasoft/propeller/PreferencesTest.java
index da8f37df..9a8cc1b9 100644
--- a/modules/spin-tools/src-tests/com/maccasoft/propeller/PreferencesTest.java
+++ b/modules/spin-tools/src-tests/com/maccasoft/propeller/PreferencesTest.java
@@ -15,6 +15,8 @@
 import java.io.ByteArrayOutputStream;
 import java.io.File;
 import java.io.StringReader;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -443,4 +445,56 @@ public void propertyChange(PropertyChangeEvent evt) {
         Assertions.assertArrayEquals(data, subject.preferences.roots);
     }
 
+    @Test
+    void testSpin1Defines() throws Exception {
+        Preferences subject = new Preferences();
+
+        Map<String, String> defines = new HashMap<>();
+        defines.put("KEY", "VALUE");
+        defines.put("EMPTY_KEY", "");
+        subject.setSpin1Defines(defines);
+
+        ByteArrayOutputStream os = new ByteArrayOutputStream();
+
+        ObjectMapper mapper = new ObjectMapper();
+        mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
+        mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
+        mapper.setSerializationInclusion(Include.NON_DEFAULT);
+        mapper.writeValue(os, subject.preferences);
+
+        Assertions.assertEquals(""
+            + "{\n"
+            + "  \"spin1Defines\" : {\n"
+            + "    \"EMPTY_KEY\" : \"\",\n"
+            + "    \"KEY\" : \"VALUE\"\n"
+            + "  }\n"
+            + "}", os.toString().replaceAll("\\r\\n", "\n"));
+    }
+
+    @Test
+    void testSpin2Defines() throws Exception {
+        Preferences subject = new Preferences();
+
+        Map<String, String> defines = new HashMap<>();
+        defines.put("KEY", "VALUE");
+        defines.put("EMPTY_KEY", "");
+        subject.setSpin2Defines(defines);
+
+        ByteArrayOutputStream os = new ByteArrayOutputStream();
+
+        ObjectMapper mapper = new ObjectMapper();
+        mapper.configure(SerializationFeature.INDENT_OUTPUT, true);
+        mapper.configure(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS, true);
+        mapper.setSerializationInclusion(Include.NON_DEFAULT);
+        mapper.writeValue(os, subject.preferences);
+
+        Assertions.assertEquals(""
+            + "{\n"
+            + "  \"spin2Defines\" : {\n"
+            + "    \"EMPTY_KEY\" : \"\",\n"
+            + "    \"KEY\" : \"VALUE\"\n"
+            + "  }\n"
+            + "}", os.toString().replaceAll("\\r\\n", "\n"));
+    }
+
 }
diff --git a/modules/spin-tools/src/com/maccasoft/propeller/EditorTab.java b/modules/spin-tools/src/com/maccasoft/propeller/EditorTab.java
index 5d10de26..27beeb0c 100644
--- a/modules/spin-tools/src/com/maccasoft/propeller/EditorTab.java
+++ b/modules/spin-tools/src/com/maccasoft/propeller/EditorTab.java
@@ -19,6 +19,7 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map.Entry;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.regex.Matcher;
@@ -57,13 +58,16 @@
 import com.maccasoft.propeller.model.ObjectsNode;
 import com.maccasoft.propeller.model.SourceProvider;
 import com.maccasoft.propeller.model.Token;
+import com.maccasoft.propeller.model.TokenStream;
 import com.maccasoft.propeller.model.VariablesNode;
 import com.maccasoft.propeller.spin1.Spin1Compiler;
 import com.maccasoft.propeller.spin1.Spin1Formatter;
 import com.maccasoft.propeller.spin1.Spin1TokenMarker;
+import com.maccasoft.propeller.spin1.Spin1TokenStream;
 import com.maccasoft.propeller.spin2.Spin2Compiler;
 import com.maccasoft.propeller.spin2.Spin2Formatter;
 import com.maccasoft.propeller.spin2.Spin2TokenMarker;
+import com.maccasoft.propeller.spin2.Spin2TokenStream;
 import com.maccasoft.propeller.spinc.CTokenMarker;
 import com.maccasoft.propeller.spinc.Spin1CCompiler;
 import com.maccasoft.propeller.spinc.Spin2CCompiler;
@@ -493,10 +497,30 @@ public void run() {
                         if (tabItemText.toLowerCase().endsWith(".spin")) {
                             compiler = new Spin1Compiler(preferences.getSpin1CaseSensitiveSymbols(), true);
                             compiler.setSourceProvider(new EditorTabSourceProvider(preferences.getSpin1LibraryPath()));
+
+                            for (Entry<String, String> entry : preferences.getSpin1Defines().entrySet()) {
+                                Token token;
+                                TokenStream stream = new Spin1TokenStream(entry.getValue());
+                                List<Token> list = new ArrayList<>();
+                                while ((token = stream.nextToken()).type != Token.EOF) {
+                                    list.add(token);
+                                }
+                                compiler.addDefine(entry.getKey(), list);
+                            }
                         }
                         else if (tabItemText.toLowerCase().endsWith(".spin2")) {
                             compiler = new Spin2Compiler(preferences.getSpin2CaseSensitiveSymbols());
                             compiler.setSourceProvider(new EditorTabSourceProvider(preferences.getSpin2LibraryPath()));
+
+                            for (Entry<String, String> entry : preferences.getSpin2Defines().entrySet()) {
+                                Token token;
+                                TokenStream stream = new Spin2TokenStream(entry.getValue());
+                                List<Token> list = new ArrayList<>();
+                                while ((token = stream.nextToken()).type != Token.EOF) {
+                                    list.add(token);
+                                }
+                                compiler.addDefine(entry.getKey(), list);
+                            }
                         }
                         else if (tabItemText.toLowerCase().endsWith(".c")) {
                             for (Node node : root.getChilds()) {
diff --git a/modules/spin-tools/src/com/maccasoft/propeller/Preferences.java b/modules/spin-tools/src/com/maccasoft/propeller/Preferences.java
index 69b21358..08119304 100644
--- a/modules/spin-tools/src/com/maccasoft/propeller/Preferences.java
+++ b/modules/spin-tools/src/com/maccasoft/propeller/Preferences.java
@@ -177,11 +177,15 @@ public SerializedPreferences() {
         public String[] spin1LibraryPath;
         public boolean spin1CaseSensitiveSymbols;
         public String spin1Template;
+        @JsonInclude(Include.NON_ABSENT)
+        public Map<String, String> spin1Defines;
 
         public String[] spin2LibraryPath;
         public boolean spin2CaseSensitiveSymbols;
         public boolean spin2ClockSetter;
         public String spin2Template;
+        @JsonInclude(Include.NON_ABSENT)
+        public Map<String, String> spin2Defines;
 
         public List<String> lru;
 
@@ -581,6 +585,22 @@ public void setSpin1CaseSensitiveSymbols(boolean spin1CaseSensitiveSymbols) {
         changeSupport.firePropertyChange(PROP_SPIN1_CASE_SENSITIVE_SYMBOLS, preferences.spin1CaseSensitiveSymbols, preferences.spin1CaseSensitiveSymbols = spin1CaseSensitiveSymbols);
     }
 
+    public Map<String, String> getSpin1Defines() {
+        return preferences.spin1Defines != null ? preferences.spin1Defines : new HashMap<>();
+    }
+
+    public void setSpin1Defines(Map<String, String> spin1Defines) {
+        if (spin1Defines.isEmpty()) {
+            preferences.spin1Defines = null;
+        }
+        else {
+            if (preferences.spin1Defines == null) {
+                preferences.spin1Defines = new HashMap<>();
+            }
+            preferences.spin1Defines.putAll(spin1Defines);
+        }
+    }
+
     public File[] getSpin2LibraryPath() {
         if (preferences.spin2LibraryPath != null) {
             List<File> l = new ArrayList<>();
@@ -634,6 +654,22 @@ public void setSpin2Template(File spin2Template) {
         preferences.spin2Template = spin2Template != null ? spin2Template.getAbsolutePath() : null;
     }
 
+    public Map<String, String> getSpin2Defines() {
+        return preferences.spin2Defines != null ? preferences.spin2Defines : new HashMap<>();
+    }
+
+    public void setSpin2Defines(Map<String, String> spin2Defines) {
+        if (spin2Defines.isEmpty()) {
+            preferences.spin2Defines = null;
+        }
+        else {
+            if (preferences.spin2Defines == null) {
+                preferences.spin2Defines = new HashMap<>();
+            }
+            preferences.spin2Defines.putAll(spin2Defines);
+        }
+    }
+
     public int[] getTabStops(Class<?> clazz) {
         int[] result = null;