diff --git a/src/main/java/pl/project13/maven/git/GitCommitIdMojo.java b/src/main/java/pl/project13/maven/git/GitCommitIdMojo.java
index ddc6e860..93ce83fd 100644
--- a/src/main/java/pl/project13/maven/git/GitCommitIdMojo.java
+++ b/src/main/java/pl/project13/maven/git/GitCommitIdMojo.java
@@ -17,30 +17,35 @@
 
 package pl.project13.maven.git;
 
+import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Charsets;
 import com.google.common.base.Function;
 import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import com.google.common.collect.Lists;
 import com.google.common.io.Closeables;
 import com.google.common.io.Files;
+
 import org.apache.maven.execution.MavenSession;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.project.MavenProject;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+
 import pl.project13.maven.git.log.LoggerBridge;
 import pl.project13.maven.git.log.MavenLoggerBridge;
 import pl.project13.maven.git.util.PropertyManager;
 
 import java.io.*;
-import java.nio.charset.Charset;
 import java.text.SimpleDateFormat;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Properties;
 
 /**
@@ -355,7 +360,7 @@ public void execute() throws MojoExecutionException {
       logProperties(properties);
 
       if (generateGitPropertiesFile) {
-        generatePropertiesFile(properties, project.getBasedir(), generateGitPropertiesFilename);
+        maybeGeneratePropertiesFile(properties, project.getBasedir(), generateGitPropertiesFilename);
       }
 
       if (injectAllReactorProjects) {
@@ -460,9 +465,9 @@ private boolean isOurProperty(@NotNull String keyString) {
   }
 
   void loadBuildTimeData(@NotNull Properties properties) {
-    Date commitDate = new Date();
+    Date buildDate = new Date();
     SimpleDateFormat smf = new SimpleDateFormat(dateFormat);
-    put(properties, BUILD_TIME, smf.format(commitDate));
+    put(properties, BUILD_TIME, smf.format(buildDate));
   }
 
   void loadShortDescribe(@NotNull Properties properties) {
@@ -520,26 +525,65 @@ void loadGitDataWithJGit(@NotNull Properties properties) throws IOException, Moj
     jGitProvider.loadGitData(properties);
   }
 
-  void generatePropertiesFile(@NotNull Properties properties, File base, String propertiesFilename) throws IOException {
-    Writer outputWriter = null;
-    File gitPropsFile = craftPropertiesOutputFile(base, propertiesFilename);
-    try {
-      Files.createParentDirs(gitPropsFile);
+  void maybeGeneratePropertiesFile(@NotNull Properties localProperties, File base, String propertiesFilename) throws IOException {
+    final File gitPropsFile = craftPropertiesOutputFile(base, propertiesFilename);
+    final boolean isJsonFormat = "json".equalsIgnoreCase( format );
 
-      outputWriter = new OutputStreamWriter(new FileOutputStream(gitPropsFile), Charset.forName("UTF-8"));
-      if ("json".equalsIgnoreCase(format)) {
-        log("Writing json file to [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
-        ObjectMapper mapper = new ObjectMapper();
-        mapper.writeValue(outputWriter, properties);
-      } else {
-        log("Writing properties file to [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
-        properties.store(outputWriter, "Generated by Git-Commit-Id-Plugin");
+    boolean shouldGenerate = true;
+
+    if (gitPropsFile.exists( )) {
+      final Properties persistedProperties;
+
+      try {
+        if (isJsonFormat) {
+          log("Reading exising json file [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
+
+          persistedProperties = readJsonProperties( gitPropsFile );
+        }
+        else {
+          log("Reading exising properties file [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
+
+          persistedProperties = readProperties( gitPropsFile );
+        }
+
+        final Properties propertiesCopy = (Properties) localProperties.clone( );
+
+        final String buildTimeProperty = prefixDot + BUILD_TIME;
+
+        propertiesCopy.remove( buildTimeProperty );
+        persistedProperties.remove( buildTimeProperty );
+
+        shouldGenerate = ! propertiesCopy.equals( persistedProperties );
+      }
+      catch ( CannotReadFileException ex ) {
+        // Read has failed, regenerate file
+        log("Cannot read properties file [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
+        shouldGenerate = true;
       }
+    }
 
-    } catch (IOException ex) {
-      throw new RuntimeException("Cannot create custom git properties file: " + gitPropsFile, ex);
-    } finally {
-      Closeables.closeQuietly(outputWriter);
+    if (shouldGenerate) {
+      Files.createParentDirs(gitPropsFile);
+      Writer outputWriter = null;
+
+      try {
+        outputWriter = new OutputStreamWriter(new FileOutputStream(gitPropsFile), Charsets.UTF_8);
+        if (isJsonFormat) {
+          log("Writing json file to [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
+          ObjectMapper mapper = new ObjectMapper();
+          mapper.writeValue(outputWriter, localProperties);
+        } else {
+          log("Writing properties file to [", gitPropsFile.getAbsolutePath(), "] (for module ", project.getName(), ")...");
+          localProperties.store(outputWriter, "Generated by Git-Commit-Id-Plugin");
+        }
+      } catch (final IOException ex) {
+        throw new RuntimeException("Cannot create custom git properties file: " + gitPropsFile, ex);
+      } finally {
+        Closeables.closeQuietly(outputWriter);
+      }
+    }
+    else {
+      log("Properties file [", gitPropsFile.getAbsolutePath(), "] is up-to-date (for module ", project.getName(), ")...");
     }
   }
 
@@ -577,6 +621,77 @@ private boolean directoryDoesNotExits(File fileLocation) {
     return !directoryExists(fileLocation);
   }
 
+  @SuppressWarnings( "resource" )
+  static Properties readJsonProperties(@NotNull File jsonFile) throws CannotReadFileException {
+    final HashMap<String, Object> propertiesMap;
+
+    {
+      Closeable closeable = null;
+
+      try {
+        final FileInputStream fis = new FileInputStream(jsonFile);
+        closeable = fis;
+
+        final InputStreamReader reader = new InputStreamReader(fis, Charsets.UTF_8);
+        closeable = reader;
+
+        final ObjectMapper mapper = new ObjectMapper();
+        final TypeReference<HashMap<String,Object>> mapTypeRef =
+          new TypeReference<HashMap<String,Object>>() {};
+
+        propertiesMap = mapper.readValue(reader, mapTypeRef);
+      } catch (final Exception ex) {
+        throw new CannotReadFileException(ex);
+      } finally {
+        Closeables.closeQuietly(closeable);
+      }
+    }
+
+    final Properties retVal = new Properties( );
+
+    for(final Map.Entry<String, Object> entry : propertiesMap.entrySet()) {
+      retVal.setProperty(entry.getKey(), String.valueOf(entry.getValue()));
+    }
+
+    return retVal;
+  }
+
+  @SuppressWarnings( "resource" )
+  static Properties readProperties(@NotNull File propertiesFile) throws CannotReadFileException {
+    Closeable closeable = null;
+
+    try {
+      final FileInputStream fis = new FileInputStream(propertiesFile);
+      closeable = fis;
+
+      final InputStreamReader reader = new InputStreamReader(fis, Charsets.UTF_8);
+      closeable = reader;
+
+      final Properties retVal = new Properties();
+
+      retVal.load(reader);
+
+      return retVal;
+    }
+    catch (final Exception ex) {
+      throw new CannotReadFileException(ex);
+    }
+    finally {
+      Closeables.closeQuietly(closeable);
+    }
+  }
+
+  static class CannotReadFileException
+    extends Exception
+  {
+    private static final long serialVersionUID = -6290782570018307756L;
+
+    CannotReadFileException( Throwable cause )
+    {
+      super( cause );
+    }
+  }
+
   // SETTERS FOR TESTS ----------------------------------------------------
 
   public void setFormat(String format) {