diff --git a/src/main/java/neqsim/thermo/system/SystemThermo.java b/src/main/java/neqsim/thermo/system/SystemThermo.java
index b1f17f325f..e0c6be2caa 100644
--- a/src/main/java/neqsim/thermo/system/SystemThermo.java
+++ b/src/main/java/neqsim/thermo/system/SystemThermo.java
@@ -236,18 +236,13 @@ public SystemInterface addFluid(SystemInterface addSystem) {
 
       if (index != -1) {
         addComponent(index, addSystem.getPhase(0).getComponent(i).getNumberOfmoles());
+      } else if (addSystem.getPhase(0).getComponent(i).isIsTBPfraction()) {
+        addTBPfraction(
+            addSystem.getPhase(0).getComponent(i).getComponentName().replaceFirst("_PC", ""),
+            addSystem.getPhase(0).getComponent(i).getNumberOfmoles(),
+            addSystem.getPhase(0).getComponent(i).getMolarMass(),
+            addSystem.getPhase(0).getComponent(i).getNormalLiquidDensity());
       } else {
-        /*
-         * if(addSystem.getPhase(0).getComponent(i).isIsTBPfraction()) {
-         * addTBPfraction(addSystem.getPhase(0).getComponent(i).getComponentName(),
-         * addSystem.getPhase(0).getComponent(i).getNumberOfmoles(),
-         * addSystem.getPhase(0).getComponent(i).getMolarMass(),
-         * addSystem.getPhase(0).getComponent(i).getNormalLiquidDensity());
-         * changeComponentName(addSystem.getPhase(0).getComponent(i).getComponentName()+ "_PC",
-         * addSystem.getPhase(0).getComponent(i).getComponentName().replaceFirst("_PC", "")); }
-         * addComponent(addSystem.getPhase(0).getComponent(i).getComponentName(),
-         * addSystem.getPhase(0).getComponent(i).getNumberOfmoles());
-         */
         addComponent(addSystem.getComponent(i));
       }
     }
diff --git a/src/test/java/neqsim/thermo/system/SystemThermoTest.java b/src/test/java/neqsim/thermo/system/SystemThermoTest.java
index e22e64c454..09e2721b45 100644
--- a/src/test/java/neqsim/thermo/system/SystemThermoTest.java
+++ b/src/test/java/neqsim/thermo/system/SystemThermoTest.java
@@ -38,4 +38,40 @@ public void testTPflash2() {
     testSystem.setPressure(110000.0, "Pa");
     assertEquals(1.1, testSystem.getPressure());
   }
+
+  /**
+   * <p>
+   * testAddFluids
+   * </p>
+   */
+  @Test
+  @DisplayName("test addFluids with pseudo component")
+  public void testAddFluids() {
+
+    neqsim.thermo.system.SystemPrEos fluid1 = new neqsim.thermo.system.SystemPrEos(298.0, 10.0);
+    fluid1.addComponent("methane", 1.0);
+    fluid1.addTBPfraction("C7", 1.0, 0.09, 0.81);
+
+    neqsim.thermo.system.SystemPrEos fluid2 = new neqsim.thermo.system.SystemPrEos(298.0, 10.0);
+    fluid2.addComponent("methane", 1.0);
+    fluid2.addTBPfraction("C7", 1.0, 0.09, 0.81);
+
+    fluid1.addFluid(fluid2);
+
+    assertEquals(2.0, fluid1.getComponent(0).getNumberOfmoles());
+    assertEquals(2.0, fluid1.getComponent(1).getNumberOfmoles());
+
+    assertEquals(2.0, fluid1.getComponent("methane").getNumberOfmoles());
+    assertEquals(2.0, fluid1.getComponent("C7_PC").getNumberOfmoles());
+
+    neqsim.thermo.system.SystemPrEos fluid3 = new neqsim.thermo.system.SystemPrEos(298.0, 10.0);
+    fluid3.addComponent("nitrogen", 1.0);
+    fluid3.addTBPfraction("C8", 1.0, 0.092, 0.82);
+
+    fluid1.addFluid(fluid3);
+
+    assertEquals(2.0, fluid1.getComponent("methane").getNumberOfmoles());
+    assertEquals(1.0, fluid1.getComponent("nitrogen").getNumberOfmoles());
+    assertEquals(1.0, fluid1.getComponent("C8_PC").getNumberOfmoles());
+  }
 }