diff --git a/src/sfizz/Opcode.h b/src/sfizz/Opcode.h
index 65436b2c..962acedd 100644
--- a/src/sfizz/Opcode.h
+++ b/src/sfizz/Opcode.h
@@ -12,6 +12,7 @@
 #include "StringViewHelpers.h"
 #include "absl/types/optional.h"
 #include "absl/meta/type_traits.h"
+#include "absl/strings/ascii.h"
 #include <string_view>
 #include <vector>
 #include <type_traits>
@@ -115,16 +116,18 @@ private:
 template <typename ValueType, absl::enable_if_t<std::is_integral<ValueType>::value, int> = 0>
 inline absl::optional<ValueType> readOpcode(absl::string_view value, const Range<ValueType>& validRange)
 {
-    const auto numberEnd = value.find_first_not_of("-1234567890.");
+    size_t numberEnd = 0;
+
+    if (numberEnd < value.size() && (value[numberEnd] == '+' || value[numberEnd] == '-'))
+        ++numberEnd;
+    while (numberEnd < value.size() && absl::ascii_isdigit(value[numberEnd]))
+        ++numberEnd;
+
     value = value.substr(0, numberEnd);
 
     int64_t returnedValue;
-    if (!absl::SimpleAtoi(value, &returnedValue)) {
-        float floatValue;
-        if (!absl::SimpleAtof(value, &floatValue))
+    if (!absl::SimpleAtoi(value, &returnedValue))
             return absl::nullopt;
-        returnedValue = static_cast<int64_t>(floatValue);
-    }
 
     if (returnedValue > std::numeric_limits<ValueType>::max())
         returnedValue = std::numeric_limits<ValueType>::max();
@@ -147,12 +150,24 @@ inline absl::optional<ValueType> readOpcode(absl::string_view value, const Range
 template <typename ValueType, absl::enable_if_t<std::is_floating_point<ValueType>::value, int> = 0>
 inline absl::optional<ValueType> readOpcode(absl::string_view value, const Range<ValueType>& validRange)
 {
-    const auto numberEnd = value.find_first_not_of("-1234567890.");
+    size_t numberEnd = 0;
+
+    if (numberEnd < value.size() && (value[numberEnd] == '+' || value[numberEnd] == '-'))
+        ++numberEnd;
+    while (numberEnd < value.size() && absl::ascii_isdigit(value[numberEnd]))
+        ++numberEnd;
+
+    if (numberEnd < value.size() && value[numberEnd] == '.') {
+        ++numberEnd;
+        while (numberEnd < value.size() && absl::ascii_isdigit(value[numberEnd]))
+            ++numberEnd;
+    }
+
     value = value.substr(0, numberEnd);
 
     float returnedValue;
     if (!absl::SimpleAtof(value, &returnedValue))
-		return absl::nullopt;
+        return absl::nullopt;
 
     return validRange.clamp(returnedValue);
 }
diff --git a/tests/OpcodeT.cpp b/tests/OpcodeT.cpp
index 53581dd6..bfd0a7f8 100644
--- a/tests/OpcodeT.cpp
+++ b/tests/OpcodeT.cpp
@@ -250,12 +250,15 @@ TEST_CASE("[Opcode] Normalization")
 TEST_CASE("[Opcode] readOpcode")
 {
     REQUIRE( sfz::readOpcode("16", sfz::Range<uint8_t>(0, 100)).value() == 16 );
+    REQUIRE( sfz::readOpcode("+16", sfz::Range<uint8_t>(0, 100)).value() == 16 );
     REQUIRE( sfz::readOpcode("110", sfz::Range<uint8_t>(0, 100)).value() == 100 );
     REQUIRE( sfz::readOpcode("-1", sfz::Range<uint8_t>(0, 100)).value() == 0 );
     REQUIRE( sfz::readOpcode("12.5", sfz::Range<int>(-100, 100)).value() == 12 );
+    REQUIRE( sfz::readOpcode("+12.5", sfz::Range<int>(-100, 100)).value() == 12 );
     REQUIRE( sfz::readOpcode("-40", sfz::Range<int>(-100, 100)).value() == -40 );
     REQUIRE( sfz::readOpcode("-140", sfz::Range<int>(-100, 100)).value() == -100 );
     REQUIRE( sfz::readOpcode("12.5", sfz::Range<float>(0.0f, 100.0f)).value() == 12.5_a );
+    REQUIRE( sfz::readOpcode("+12.5", sfz::Range<float>(0.0f, 100.0f)).value() == 12.5_a );
     REQUIRE( sfz::readOpcode("-22.5", sfz::Range<float>(-20.0f, 100.0f)).value() == -20.0_a );
     REQUIRE( sfz::readOpcode("150.5", sfz::Range<float>(-20.0f, 100.0f)).value() == 100.0_a );
     REQUIRE( sfz::readOpcode("50.25garbage", sfz::Range<float>(-20.0f, 100.0f)).value() == 50.25_a );