diff --git a/src/main/scala/millfork/CompilationOptions.scala b/src/main/scala/millfork/CompilationOptions.scala
index 6e94b850..564da98d 100644
--- a/src/main/scala/millfork/CompilationOptions.scala
+++ b/src/main/scala/millfork/CompilationOptions.scala
@@ -75,7 +75,7 @@ object CompilationFlag extends Enumeration {
   // compilation options:
   EmitIllegals, EmitCmosOpcodes, DecimalMode, ReadOnlyArrays, PreventJmpIndirectBug,
   // optimization options:
-  DetailedFlowAnalysis, DangerousOptimizations, InlineFunctions,
+  DetailedFlowAnalysis, DangerousOptimizations, InlineFunctions, OptimizeForSize, OptimizeForSpeed,
   // memory allocation options
   VariableOverlap, CompactReturnDispatchParams,
   // runtime check options
diff --git a/src/main/scala/millfork/Main.scala b/src/main/scala/millfork/Main.scala
index b4683a7f..79cabc44 100644
--- a/src/main/scala/millfork/Main.scala
+++ b/src/main/scala/millfork/Main.scala
@@ -225,7 +225,15 @@ object Main {
     }
     flag("--inline").action { c =>
       c.changeFlag(CompilationFlag.InlineFunctions, true)
-    }.description("Inline functions automatically (experimental).")
+    }.description("Inline functions automatically.")
+    flag("-Of", "--fast").action { c =>
+      c.changeFlag(CompilationFlag.OptimizeForSize, false)
+      c.changeFlag(CompilationFlag.OptimizeForSpeed, true)
+    }.description("Optimize for speed (experimental).")
+    flag("-Os", "--size").action { c =>
+      c.changeFlag(CompilationFlag.OptimizeForSize, true)
+      c.changeFlag(CompilationFlag.OptimizeForSpeed, false)
+    }.description("Optimize for size (experimental).")
     flag("--detailed-flow").action { c =>
       c.changeFlag(CompilationFlag.DetailedFlowAnalysis, true)
     }.description("Use detailed flow analysis (experimental).")
diff --git a/src/main/scala/millfork/output/Assembler.scala b/src/main/scala/millfork/output/Assembler.scala
index 75b95792..d466c671 100644
--- a/src/main/scala/millfork/output/Assembler.scala
+++ b/src/main/scala/millfork/output/Assembler.scala
@@ -145,7 +145,11 @@ class Assembler(private val program: Program, private val rootEnv: Environment)
     val assembly = mutable.ArrayBuffer[String]()
 
     val potentiallyInlineable: Map[String, Int] =
-      InliningCalculator.getPotentiallyInlineableFunctions(program, options.flags(CompilationFlag.InlineFunctions))
+      InliningCalculator.getPotentiallyInlineableFunctions(
+        program,
+        options.flags(CompilationFlag.InlineFunctions),
+        if (options.flags(CompilationFlag.OptimizeForSpeed)) 1.3 else 1.0,
+        if (options.flags(CompilationFlag.OptimizeForSpeed)) 8.0 else 1.2)
 
     var inlinedFunctions = Map[String, List[AssemblyLine]]()
     val compiledFunctions = mutable.Map[String, List[AssemblyLine]]()
diff --git a/src/main/scala/millfork/output/InliningCalculator.scala b/src/main/scala/millfork/output/InliningCalculator.scala
index a7ebe86d..cd12ad79 100644
--- a/src/main/scala/millfork/output/InliningCalculator.scala
+++ b/src/main/scala/millfork/output/InliningCalculator.scala
@@ -16,8 +16,8 @@ object InliningCalculator {
 
   def getPotentiallyInlineableFunctions(program: Program,
                                         inlineByDefault: Boolean,
-                                        aggressivenessForNormal: Double = 1.0,
-                                        aggressivenessForRecommended: Double = 1.2): Map[String, Int] = {
+                                        aggressivenessForNormal: Double,
+                                        aggressivenessForRecommended: Double): Map[String, Int] = {
     val callCount = mutable.Map[String, Int]().withDefaultValue(0)
     val allFunctions = mutable.Set[String]()
     val badFunctions = mutable.Set[String]()