diff --git a/app/src/main/java/org/solovyev/android/calculator/AcraErrorReporter.java b/app/src/main/java/org/solovyev/android/calculator/AcraErrorReporter.java
index 3242fde8..68b9e103 100644
--- a/app/src/main/java/org/solovyev/android/calculator/AcraErrorReporter.java
+++ b/app/src/main/java/org/solovyev/android/calculator/AcraErrorReporter.java
@@ -22,6 +22,7 @@
 
 package org.solovyev.android.calculator;
 
+import android.util.Log;
 import org.acra.ACRA;
 
 import javax.annotation.Nonnull;
@@ -33,6 +34,7 @@ public class AcraErrorReporter implements ErrorReporter {
     @Override
     public void onException(@Nonnull Throwable e) {
         if (!ENABLED) {
+            Log.e("Acra", e.getMessage(), e);
             return;
         }
         ACRA.getErrorReporter().reportBuilder().forceSilent().exception(e).send();
@@ -41,6 +43,7 @@ public class AcraErrorReporter implements ErrorReporter {
     @Override
     public void onError(@Nonnull String message) {
         if (!ENABLED) {
+            Log.e("Acra", message);
             return;
         }
         ACRA.getErrorReporter().reportBuilder().forceSilent().exception(new Throwable(message)).send();
diff --git a/app/src/main/java/org/solovyev/android/calculator/BaseEntitiesRegistry.java b/app/src/main/java/org/solovyev/android/calculator/BaseEntitiesRegistry.java
index fc221cc9..12ead3dd 100644
--- a/app/src/main/java/org/solovyev/android/calculator/BaseEntitiesRegistry.java
+++ b/app/src/main/java/org/solovyev/android/calculator/BaseEntitiesRegistry.java
@@ -47,6 +47,12 @@ public abstract class BaseEntitiesRegistry<T extends MathEntity, P extends Persi
     @Nullable
     protected final EntityDao<P> entityDao;
 
+    @Nonnull
+    protected final Object lock = this;
+
+    // synchronized on lock
+    private boolean initialized;
+
     protected BaseEntitiesRegistry(@Nonnull MathRegistry<T> mathRegistry,
                                    @Nonnull String prefix,
                                    @Nullable EntityDao<P> entityDao) {
@@ -125,6 +131,20 @@ public abstract class BaseEntitiesRegistry<T extends MathEntity, P extends Persi
             // just in case
             Locator.getInstance().getErrorReporter().onException(e);
         }
+        setInitialized();
+    }
+
+    protected final void setInitialized() {
+        synchronized (lock) {
+            Check.isTrue(!initialized);
+            initialized = true;
+        }
+    }
+
+    public boolean isInitialized() {
+        synchronized (lock) {
+            return initialized;
+        }
     }
 
     @Nonnull
diff --git a/app/src/main/java/org/solovyev/android/calculator/FunctionsRegistry.java b/app/src/main/java/org/solovyev/android/calculator/FunctionsRegistry.java
index 57fb8209..db5482ac 100644
--- a/app/src/main/java/org/solovyev/android/calculator/FunctionsRegistry.java
+++ b/app/src/main/java/org/solovyev/android/calculator/FunctionsRegistry.java
@@ -104,16 +104,18 @@ public class FunctionsRegistry extends BaseEntitiesRegistry<Function, OldFunctio
         Check.isNotMainThread();
         migrateOldFunctions();
 
-        add(new CustomFunction.Builder(true, "log", Arrays.asList("base", "x"), "ln(x)/ln(base)"));
-        add(new CustomFunction.Builder(true, "√3", Collections.singletonList("x"), "x^(1/3)"));
-        add(new CustomFunction.Builder(true, "√4", Collections.singletonList("x"), "x^(1/4)"));
-        add(new CustomFunction.Builder(true, "√n", Arrays.asList("x", "n"), "x^(1/n)"));
-        add(new CustomFunction.Builder(true, "re", Collections.singletonList("x"), "(x+conjugate(x))/2"));
-        add(new CustomFunction.Builder(true, "im", Collections.singletonList("x"), "(x-conjugate(x))/(2*i)"));
+        addSafely(new CustomFunction.Builder(true, "log", Arrays.asList("base", "x"), "ln(x)/ln(base)"));
+        addSafely(new CustomFunction.Builder(true, "√3", Collections.singletonList("x"), "x^(1/3)"));
+        addSafely(new CustomFunction.Builder(true, "√4", Collections.singletonList("x"), "x^(1/4)"));
+        addSafely(new CustomFunction.Builder(true, "√n", Arrays.asList("x", "n"), "x^(1/n)"));
+        addSafely(new CustomFunction.Builder(true, "re", Collections.singletonList("x"), "(x+conjugate(x))/2"));
+        addSafely(new CustomFunction.Builder(true, "im", Collections.singletonList("x"), "(x-conjugate(x))/(2*i)"));
 
         for (CppFunction function : loadFunctions()) {
-            add(function.toCustomFunctionBuilder());
+            addSafely(function.toCustomFunctionBuilder());
         }
+
+        setInitialized();
     }
 
     @Override
@@ -124,13 +126,26 @@ public class FunctionsRegistry extends BaseEntitiesRegistry<Function, OldFunctio
     }
 
     @Override
-    public Function add(@Nonnull JBuilder<? extends Function> result) {
-        final Function function = super.add(result);
-        // todo serso: don't save while we're initializing
-        save();
+    public Function add(@Nonnull JBuilder<? extends Function> builder) {
+        final Function function = super.add(builder);
+        if (isInitialized()) {
+            save();
+        }
         return function;
     }
 
+    @Nullable
+    public Function addSafely(@Nonnull JBuilder<? extends Function> builder) {
+        try {
+            // todo serso: currently JSCL might produce function's body which can't be loaded afterwards. F.e. f(x) = 3 * 6
+            // might be simpliffied to f(x) = 18 × 10 ^ 0 and × is not supported by JSCL
+            return add(builder);
+        } catch (Exception e) {
+            errorReporter.onException(e);
+        }
+        return null;
+    }
+
     @NonNull
     private List<CppFunction> loadFunctions() {
         try {
@@ -151,6 +166,7 @@ public class FunctionsRegistry extends BaseEntitiesRegistry<Function, OldFunctio
             final OldFunctions oldFunctions = serializer.read(OldFunctions.class, xml);
             if (oldFunctions != null) {
                 List<CppFunction> functions = OldFunctions.toCppFunctions(oldFunctions);
+                // todo serso: fix multiplication sign issue
                 FileSaver.save(getFunctionsFile(), Json.toJson(functions).toString());
             }
             preferences.edit().remove(OldFunctions.PREFS_KEY).apply();
diff --git a/app/src/main/java/org/solovyev/android/calculator/KeyboardUi.java b/app/src/main/java/org/solovyev/android/calculator/KeyboardUi.java
index 2268ccda..5ce9612e 100644
--- a/app/src/main/java/org/solovyev/android/calculator/KeyboardUi.java
+++ b/app/src/main/java/org/solovyev/android/calculator/KeyboardUi.java
@@ -49,6 +49,8 @@ public class KeyboardUi {
     private final int sidePadding;
     @DrawableRes
     private final int buttonBackground;
+    @NonNull
+    private final String multiplicationSign = Locator.getInstance().getEngine().getMultiplicationSign();
 
     @SuppressWarnings("deprecation")
     public KeyboardUi(@NonNull User user, @NonNull List<String> parameterNames) {
@@ -110,7 +112,7 @@ public class KeyboardUi {
         addButton(row, 0, "7");
         addButton(row, 0, "8");
         addButton(row, 0, "9").setText("π", up).setText("e", down);
-        addOperationButton(row, R.id.cpp_kb_button_multiply, Locator.getInstance().getEngine().getMultiplicationSign()).setText("^n", up).setText("^2", down);
+        addOperationButton(row, R.id.cpp_kb_button_multiply, multiplicationSign).setText("^n", up).setText("^2", down);
         addButton(row, R.id.cpp_kb_button_clear, "C");
 
         row = makeRow();
@@ -264,7 +266,7 @@ public class KeyboardUi {
                     user.insertOperator('-');
                     break;
                 case R.id.cpp_kb_button_multiply:
-                    user.insertOperator('*');
+                    user.insertOperator(multiplicationSign);
                     break;
                 case R.id.cpp_kb_button_functions_constants:
                     user.showFunctionsConstants(v);
diff --git a/app/src/main/java/org/solovyev/android/calculator/function/CppFunction.java b/app/src/main/java/org/solovyev/android/calculator/function/CppFunction.java
index 976548b5..b3675ac5 100644
--- a/app/src/main/java/org/solovyev/android/calculator/function/CppFunction.java
+++ b/app/src/main/java/org/solovyev/android/calculator/function/CppFunction.java
@@ -235,6 +235,13 @@ public class CppFunction implements Jsonable, Parcelable {
             return this;
         }
 
+        @Nonnull
+        public Builder withBody(@NonNull String body) {
+            Check.isTrue(!built);
+            function.body = body;
+            return this;
+        }
+
         @Nonnull
         public CppFunction build() {
             built = true;